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.
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.
> Once you start down the road of being dictotoe of spending on expensive things that aren't solving starvation, all kinds of things like space exploration, the development of the internet, etc all become "sorry effects". Guess how many villages could be fed on the budget of the Apollo program.
I do not advocate dictating spending but propose designing a better incentive system for rich people to spend money on useful things. See my reply to another comment down below.
What are ‘useful’ things?
Your examples here have good probabilities of turning into ‘utility’ for the masses. Cure of cancer (obvious), Apollo program (many scientific advances), ...
Bidding up prestige and coolness is a zero sum game and only increases a small bit of satisfaction of a few rich people.
It is about valuing the needs of the rich and the masses more equitably.