I fundamentally disagree. You have to ignore a lot of expectations and nuances of human behavior and social interactions to reduce an incomplete trilogy to a hammer purchase.

I vehemently, fundamentally disagree. I don't see us bridging this gap any time soon, so best we agree to disagree on this point.

Here's a better example... I buy a Playstation 5 for $500... it comes with one game. I buy it with the expectation that I will be able to buy further games in the future, as the company advertises. If those never happen, did I get cheated? From a legal, contractual sense, no. I agreed to a purchase and made it. Will I ever buy anything from Playstation again? No, because they promised something and didn't deliver, causing me to not get the value I expected from my $500 purchase.

I see an advertised book series alot like that. Yes, I bought a single book for an agreed price. The book may end on an unsatisfying cliffhanger. I may even know this ahead of time, but I'm OK with it because the author and his publisher have promised it is the first part of a series I think I will enjoy. If the series never concludes, of course I'm going to upset about it, and it will color my opinion of the work.

Does that give fans the right to harass anyone? Of course not. But if the writer expects to have any sort of fans in the future, common sense says they should do what they say, close to when they say it. Stuff comes up to cause delays, of course. People in general are pretty OK with that. (I don't see too fans of the various TV shows that have been COVID delayed rioting). To just fail to meet expectations without an explanation, or a plan, or remorse, to the point where you refuse to discuss it? That's just wrong IMO.

I don't think it's a better one, just different as it amounts to the same: You paid 500 dollars and got a system and a game with a market value of 500 dollars nothing more and nothing less.

Now, if no other games were ever made you're free to feel disappointed(that's natural) and you're free to decide not to buy other consoles from that company based on your experience...but when you go further than that and say you're owed more, that there is an obligation to the fans to finish the story then that's entitlement pure and simple. 

And again, if the author doesn't offer up an explanation for the delay, doesn't want to answer questions about it or offer an apology? So what? Again, you're not owed any of those things and if you think you are then once again that's being entitled. The publisher is owed those things because they contracted the author to write x amount of books...but you aren't owed anything more than the book you got with your 20 bucks.

Again, it's normal to be disappointed and frustrated but when you take it beyond that you're in the wrong and there really is no other way to see it.

Sure, unforeseeable accidents or changes in circumstances are certainly defensible reasons for not continuing. Is that what you're talking about? Writer's block seems less of an excuse to me - perhaps if you don't have a firm plan you shouldn't commit to such a project in the first place. And if the reader knew in advance the writer isn't committed to finishing the story they would probably save themselves the trouble of starting to read it. This seems quite reasonable to me. I'm surprised there's even any argument about it!

Sorry, I was in a rotten mood yesterday that had nothing to do with anyone here. Trying this again.

This is where I disagree and where I think the problem comes in. If you reduce this exchange to just the actual transaction in a bubble (exchange money for a console and a game) you are ignoring the context and background in which it took place. This view doesn't reflect reality. Sony wasn't selling just a game console and a game for $500. They were selling a game, a game console that could play it and many other future games, and the potential to buy future games on it. The context isn't background info; it is vital to the point.

For background, video game consoles have been around forever. Widespread household adoption of gaming consoles has been around in at least the last 4 consecutive decades. There have been dozens, and all of the major ones have all followed the same basic structure. You get one machine that can play lots of games that you buy individually. This has been true for decades. Every sane customer in a country where game consoles are sold knows this. This is such widespread knowledge that you can take it for granted. It is Common Knowledge™.

For over 20 years, the Sony Playstation brand in particular has been immensely popular and wildly successful among those consoles. Every one of those consoles before the PS5 in this example have worked this same way: you buy this one expensive machine that can play lots of games that will come out. Everyone knows this. This is Common Knowledge™ and taken for granted.

Now Sony comes out with a new Playstation 5 with one game available at launch. Sony advertises this as the next generation of Playstation console and it is launching with this game. Everyone knows how Playstations work because it is Common Knowledge™, and Sony knows that people know how they work and what to expect because it is Common Knowledge™. If Sony advertises as usual, no one would have any reason to believe no more games would be offered for sale. If Sony never offers more games for sale and never makes this clear in the advertising or promotion, if they just allowed consumers to believe it would be like past consoles without a warning, were they in the wrong? Absolutely, yes. They took advantage of Common Knowledge™ for their benefit. They sold on the basis of Common Knowledge™ but failed to deliver, and never told anyone they were changing the rules.

The point is that they will have gotten the benefit of the Common Knowledge™ and everyone's understanding of game consoles to sell more systems and then never deliver on the understanding of more games, either unspoken in the case of everyone knowing how they work, or spoken if they advertise as more games coming. They took advantage of people.

Virtually no one would pay $500 for a game console they knew up front would only ever have one game, and Sony knows this. If they knowingly allow customers to buy the console assuming there will be many games, but they know otherwise and never tell them, that is absolutely wrong. Even if Sony intended to release more games but somehow it falls through legally, Sony would ruin their reputation as being unable to deliver or get it done.

No reasonable person would ever imagine for a moment that Sony would sell a full price new console that would only ever play one game, and if they were allowed (or even led) to believe there would be more, they would have every right to feel swindled. You might say "Well, Sony never technically guaranteed there would be more games, so you only have yourself to blame for expecting more" which is reductive to the point of absurdity. And who in the history of anything has ever felt good after being deprived of something out of some minor technicality?

As has been discussed in the thread, Sony might not be in violation in any kind of legally binding contractual sense*, but they absolutely would be in a moral sense or respect of their customers sense. They would rightfully destroy their reputation, and I for one would go out of my way to never buy a Sony product again as long as I could do it. Basically, they will have quite literally taken advantage of the Common Knowledge™ everyone has of how game consoles work to lead people into buying something they otherwise would not have if they had been properly informed up front.

Onto creative works, it's not exactly the same, but some degrees of the points are applicable. Let's say I am a theoretical author who is writing a five part fantasy epic, and I promote
and advertise it as such. I might have a few other series under my belt and people know who I am. This one takes off, and I have no issues becoming rich and famous off my book sales, spin off TV adaptations, etc, all the time still promoting it as a 5 part series. Everyone knows how book series work and reasonably expects an endpoint eventually. Say after the 3rd book, I get tired of writing. I would much rather spend my time living the high life and being rich, and I eventually squeeze out part 4, but you can tell I'm bored with it and it's not up to par. I never get around to finishing the last book, and my fans are frustrated and pissed off. They feel I committed to completing the series since I advertised is as a 5 part series, and they feel cheated that I am never going to finish. They resent buying the previous books, watching the show, buying merchandise, seeing me at conventions, etc, Is this solely their fault for expecting a 5th book eventually? Do I have no culpability in this situation? I had no problem taking their money selling the story under the pretext they would get the ending some day, but I never technically included a legal contract with each book guaranteeing them the next installment if they paid, so did I really do anything wrong?

It might not be breaking any hard legal obligation, but to put it in the vernacular, that's a dick move. In any case, only doing what you are legally obligated to do is not a great criterion for evaluating morality.

* If they actually advertised it as having more and then never delivered, then they probably would even be at fault in a legal sense, too. At least in the EU which has very strict consumer protection laws

It may be a "dick move" and one can be disappointed, and it's certainly not a sound business strategy on their part if they want to sell another story...but it still doesn't mean you're entitle to more than you paid for.