Dermot Mulroney was furious when he exchanged gifts with his The Family Stone co-star LUKE WILSON - because he was convinced he'd spent far more.

Mulroney opted for the generous approach, handing his pal a stack of money - only to receive an ornament in return.

He says, "I gave Luke a cheque for $1,000 and he gave me a paperweight. It's handsome, and holds my papers down."

But Wilson explains, "Oddly enough, the paperweight was like 950 bucks, so we kind of broke even."