It really depends on the agent. I was returning from a 7 day cruise with my family in FLL in Y, and all six of our checked bags were over 50lbs, the heaviest being 54lbs, but the agent did not charge us for the bags (she did place a heavy tag on them). On the other hand, I was flying international J from EWR and one bag was one pound over while my other was ten pounds under and the agent made me transfer one pound to the lighter bag.