NM 98 exploded about 4-5 years ago though, long before the solo movie was announced, but after the appearance in Wolverine Origins appearance. Overstreet took forever to catch up. The books was selling for cons easily for $100 and Overstreet had it as a $20-30 book. When Overstreet upped it to $100 it was already going for $25-300 at cons. Last Gem City I went, one dealer  I know had 10 copies of 9.0 or better and sold all 10 in the first hour of the first day of the show, none for less than $250 and he kept track afterwards and had 37 more requests for the book the first day. He didn't track day 2, but got several more requests for the book. He basically said if had 100 copies, he could have easily sold all 100 for that price. People weren't batting an eye or haggling for it, just coughing up to get it. This usually is a sign there is room for a lot more growth for the book because demand is very high, and even though it was a plentiful book, not as many are making it to market as you may think. I don't think the book has hit it's ceiling yet, and I don't think it's going to fade fast once it does. It may correct itself a bit, but I don't see the bottom dropping out on this one. 

-M