Billionaire art collector Ronald Perelman sued mega-art dealership Gagosian Gallery in New York State Supreme Court in Manhattan on Sept. 12. That same day, Gagosian Gallery filed a lawsuit against Perelman claiming he refused to pay for artworks.

Perelman's suit against dealer Larry Gagosian and his gallery alleges that he concealed material information and used his position in the art world to manipulate the price of artwork.

Among the complaints over tens of millions of dollars worth of art, Perelman claims that Gagosian had him buy Jeff Koons' Popeye sculpture for $4 million, payable in 5 installments.

The collector says that secret contract provisions that the gallery had with the artist were not disclosed and that such "restrictions effectively crippled plaintiffs’ ability to resell Popeye at its fair market value."

Gagosian's complaint says that Perelman's non-payments and forceful barters have cost the gallery millions of dollars, made it pay artists out of its own capital and lose commissions.