Quote from Phoebe in The One with the Ball
Monica: So you're moving in with him? What happened? Phoebe: I couldn't tell him no. He got so sad. Maybe it'll be all right. I do really like him a lot and probably do it eventually, anyway. And, plus, think of all the money I'll save on stamps. Monica: Why, do you write him a lot? Phoebe: No. I just heard when people live together they split the cost of stamps, don't they? Ross: Yeah, yeah.