"Pawn Stars" badass Austin "Chumlee" Russell made one hell of a birthday negotiation at a nightclub this weekend -- You give me 40 bottles of Cristal ... I'll give you $11 THOUSAND DOLLARS!!
Chumlee rolled into Push nightclub in Tunica, Mississippi on Saturday night -- and decided he wanted to treat the entire place to some fancy champagne ... so he did.
Chum -- who was hanging with "Pawn Stars" bodyguard Antoine -- racked up a total bill of $9,558 ... and then dropped a $2,000 tip ... for a grand total of $11,558.
Wonder what the Old Man would say ...