KIM KARDASHIAN HAS TO PAY KRIS HUMPHRIES TO KEEP RING

Kim Kardashian is going to shell out some serious dough so she can keep her MASSIVE engagement ring ... and TMZ has learned, the cash is all going to Kris Humphries.

Sources close to the former couple tell us ... it was Kris who originally bought the 20.5 carat diamond stunner ... and Kim loved the ring so much, she included a clause in the pre-nup which allows her buy the ring from Kris for the original purchase price in the case of a divorce.