I mean, if I had this book I would definitely wait for the first trailer that showed X-23 or some kind of solid confirmation before unloading this. Movie spikes are just a thing that we as collectors are going to have to deal with until the market corrects itself. Even look at NM98. It's lost approximately 35-40% of its value in CGC 9.8 from the peak of $1000-1200. It can now be had on eBay for under $700.
It's a bubble. It sucks as a collector or a buyer, but is good for sellers. Me as a collector without a lot of capital just has to wait a few more years before the market corrects itself and speculators start unloading these books for decent (read: normal) prices.
There's no way to realistically short or bet against these kind of prices continuing, so the only sane thing to do as a collector is to sit back, save up and buy these books at a discount when the market crashes. I don't believe it will be as bad as the 1990s crash, but it will be painful for some speculators for certain.