The market's collapsing for the same reason as the subprime crisis: too much borrowed money fueled a bubble, and now it's unwinding. People buying comics on credit cards, layaway plans, etc. -- everyone's a dealer -- all thinking they could flip the books anytime for more than they paid. That only works in a rising market. Once the comic prices stopped rising, the speculators and fast money shifted into video games, further depressing the comic prices.
And the remaining buyers only want to cherry pick the cream of the crop - good page quality, no chipping, no writing, etc. It's simply not enough to just own a coveted key anymore (with the exception of certain grails, like Tec 27 and Action 1), the book has to be nearly perfect. This is due to some OCD fool that started nit picking wrap centering, page quality, chipping and other previously irrelevant attributes. That terrible trend caught on like fire, and now all the remaining buyers only want the best. Collectors like me, that used to be happy just owning a book, are now forced to seek out the best, not because we're looking to sell or really care that there's a chip in a book, but because if you ever want/need to sell it, only the perfect copies sell for full value. For example, look at all the orphaned copies of AF15 on eBay that will never catch a bid. Some are beautiful, but because their page quality is cream or they have chipping, they are pariah.
Not a good combination.