It's part fashion, it's part bubble, it's part QE. But the people driving up the prices are just regular guys buying the cars they've wanted for a while. Once supply dwindles, price goes up and creates a positive feedback loop.
It will all calm back down in a few years, where values will stay is anyones guess.
The custom motorcycle scene is a good example of this. So much new stuff flooded the market and everyone, including the new guys got bored. The shift to the old vintage and "garage" built stuff became the new hotness and now the old guard are having to pay stupidly high prices for half a cracked case and two burnt out pistons.
New comers with money buy up everything. Eventually though, either they don't have a clue what they are doing and/or give up soon after and just store the shit with the other failed quarter/mid life crisis dreams.
Like you though, it might be sour grapes.