However, an auction house is going to take significant fees as a percentage of the sale price and your shill bidder will want a cut as well. You’re also going to get a large tax bill because you technically had a realized capital gain and the auction house will report it.
With NFTs you can do a blockchain transaction for a relatively small fee by yourself from your computer. No taxes owed because you didn’t actually sell anything.
Isn't it basically a flat tax, not dependent on the value "claimed" by the transaction, that is easily drowned for any transaction that would make such a scam worthwhile anyway?
Yes, and it's rampant in all sorts of collectibles markets. There are some people doing it very publicly with vintage video game cartridges right now, and "pawn stars"-type game shows are largely marketing for the scam.
Yes, but the auction house takes a cut and the taxman might notice so it's not without risk. Usually a shill bidder doesn't want to win the actual bid.