There are the rich, the very rich, and the superrich that are so superrich that they are absolutely beyond the pale, to which most people are absolutely clueless as to how the world of the wealthy actually revolves. The world is a very large place to which money is made in all sorts of ways, some legal, some not, some of very questionable actions, some not, and some of blatantly illegal ways, and some not. Those that make their money on the "dark side", so to speak, have only solved half the equation, as cash or cash like instruments, in and of itself, has limited value if you are unable to turn that cash into something of more tangible value, especially something that is both fungible as well as easily transferrable and preferably of international merit.
The big auction houses such as Christie's and Sotheby's have taken over from the Swiss bankers of old, as the new way to laundry and store money that has questionable origins. The first clue that Christie's and Sotheby's are not on the up and up, is the fact that some of the most expensive art pieces in the history of mankind are sold or transferred to either straight-out anonymous parties, that "prefer for privacy reasons" not to be identified, or sold to a named person or rumored to have been sold to a named person in the art industry, who in fact is just a front for an anonymous buyer.
The second clue that things at Christie's and Sotheby's are not on the up and up, is revealed within the increasingly insane pricing of art pieces that are sold. For instance, a Cezanne painting sells for $250 million, and a Picasso for $155 million, and the still living Jasper Johns painting goes for $110 million. No matter how you slice and dice the pricing on these pieces, none of these pieces demand that type of pricing, yet prices like these or on a somewhat smaller scale are achieved again and again and again.
Because a given art piece must have a buyer as well as a seller, and of course, be able to accommodate the very nice commission for the art gallery or auction selling the piece, there has to be some sort of assurance for all parties involved, that the punch bowl in regards to these high-end art pieces is not going to be taken away anytime soon. That bowl is primarily controlled and manipulated by the art auction houses themselves in conjunction with certain art critics and the credulous press. That is to say, you are not going to get buyers, with even the most corrupt and dirty money, even considering buying art, if they aren't confidently reassured that the art game itself is rigged in everybody's favor.
For instance, if there is an agreement, an implied agreement, of course, that art pieces will always or almost always go up in price over time, this makes the dealing of this commodity much more enticing for those that need to wash their dirty money and thereby to cleanse it, from either a buying or selling perspective, as today's buyer, is often tomorrow's seller, and that washing cycle continues until such time as the game can no longer sustain itself. So despite what you might hear from the art experts, or despite the denials from Sotheby's and Christie's, today's art pricing is a manipulated shell game, rigged, and fueled significantly by the very dirty money hiding behind the cloak of anonymity, tax evasion, and/or false fronts.