Billionaire Dmitry Rybolovlev has spent years filing lawsuits around the world against dealer Yves Bouvier, whom Rybolovlev accuses of charging outrageous markups on dozens of artworks. (Among those works is Leonardo da Vinci’s Salvator Mundi, which Rybolovlev bought via Bouvier in 2013 and on which he made more than $320 million in profit when he auctioned it off last year.) Bouvier is not named in this particular legal complaint, which accuses Sotheby’s of knowing about the markups Bouvier was charging in the sales the auction house assisted in. (Rybolovlev, by the way, is the oligarch who purchased a Palm Beach mansion sight-unseen from Donald Trump for $95 million, by far the highest price ever paid for a home in the Florida resort town.)