supply
when a book gets hot what usually seems to happen is
1. People pull their mid-high grade slabs from the market (ebay, websites, even physical stores) to see how high it will go so they can get top dollar.
2. People start going through their long boxes of dreck to see if they have it, and if they do they "cash out" selling at above market prices as they "ride the wave" of the books inflation.
3. Some of those people send decent/higher grade raws off to CGC so theres a month or two lull as new inventory (that intends to sell) gets slabbed.
4. As those raw issues return to the owners they usually put them on the market, and we start to see supply creep up to meet the demand.
5. At that point those original holders back at #1 decide that if the market has topped off, and worry about the influx of availability and they decide to sell their copies too (unless they think its gonna keep rising, at which point they continue to hold)
this seemed to happen with IM55 and many other "movie" related books...
A fine summary.
The moment there is a sniff of a movie connection --- speculators go crazy and everyone becomes a speculator.
As the entire Marvel Universe will soon be on film -- every Marvel comic book will be a key -- which entitles every book to be very expensive regardless of intrinsic merit.
And three sumos just because ...