As someone with a bit of knowledge of economics and business, what happens in overpriced markets is a "hollowing out" effect. A price is set for a particular piece (generally based on market conditions which existed at one time), but no one else buys it at that price. The potential seller thinks the piece should sell for that amount, because another one had done so once before, and he/she won't lower it. So it stays off the market--until the seller has so much money tied up in inventory he has to sell at "depressed" prices. That's the "collapse" in the phrase "overshoot and collapse". Everything falls apart sharply (like with the Dutch tulip bulbs).
I once spoke to a dealer in Persian rugs who had a "specimen" piece he bought in the 1980's and which was then worth over $1,000,000, he said. I knew the market for regular oriental rugs has dropped about 30% since then (due to oversupply, more so than "loss of interest"). He also admitted that at current prices, he didn't think he could get $500,000. But, he was willing to hold onto it because he wanted his price. Logically, that doesn't make sense, but that's the way it works.
And, there are already whiffs of it. About 5 years ago, I saw a Neil Adams cover I liked. The dealer wanted $25,000 for it, which he said at the time was really high (no, it wasn't a Batman or GL/GA cover). The dealer is still holding it, but now he wants $80,000 for it because of the price of other Adams covers. By failing to turn over inventory to meet market, he's lost the opportunity to make profits on interim deals, and is essentially taking a piece off the market.
So, while "sell, sell sell" makes sense, it won't likely happen until things get really, really off-kilter.