You do realize that the owners of the things they sell are the ones who commission then to sell their things for them, right?

Anyway, the problem isn’t auction houses, it’s the ultra-wealthy driving prices of the things they desire to insane levels. And the reason it’s a problem is because those prices are totally artificial and grossly inflated, solely for said ultra-wealthy to hide their wealth in the artificially expensive things they buy and avoid paying taxes that would benefit you and me and the whole of society.