Mathematical Expectation

I've been reading about mathematical expectation. It advocates calling when you have a positive value(coin flip example). I haven't seen or heard anyone address the amount of money that is won or lost though. What I mean is if a play is a positive value and you call all in and lose $200. Then the next three times you have the same situation you call all in for $40 each you won three times but only $120, when you lost $200 on the first hand. Does anyone address the different values of specific pots in positive expected value situations?