That money doesn't just vanish though. It's a wealth transfer from Adam to Bernice. Adam's bank balance drops from £100m to £99m, Bernice's goes from £100m to £101m.
If that transfer didn't happen, then both bank balances would remain at £100m. Nothing is lost or gained, it's irrelevant (Although in Banksy's case the original first sale often involves a transfer of wealth from Adam and Bernice to a random person)
There's nothing inherently good or bad about rich people playing money games with each others assets, it's not the same as Adam paying £10m to destroy a town and gain £20m in profit from exploiting the resources, or indeed divert tens of thousands of high-skilled effort per month into something like the Apollo program.
Any transaction costs go to paying the auction house for things like catering, electricity, security, rent etc. No worse than a bunch of rich people spending money at a restaurant.
There's an argument that auction houses aren't paying their way for the services they use (especially in expensive areas), and other functions occupying that space could be better for society. A land value tax would solve that. I'm not aware that auction houses rely on other things like copyright or patents that can stifle economic activity.
If that transfer didn't happen, then both bank balances would remain at £100m. Nothing is lost or gained, it's irrelevant (Although in Banksy's case the original first sale often involves a transfer of wealth from Adam and Bernice to a random person)
There's nothing inherently good or bad about rich people playing money games with each others assets, it's not the same as Adam paying £10m to destroy a town and gain £20m in profit from exploiting the resources, or indeed divert tens of thousands of high-skilled effort per month into something like the Apollo program.