For a certain product, the net contribution can be seen as Net Contribution = $500,000Q - $200,000, where Q is the market share.  The expected market share (E(Q)) is then substituted into the net contribution equation-->  E(Net Contribution) = $500,000E(Q) - $200,000.

Why can this be done?  In other words, the expected net contribution is the sum of all possible contribution values (ContValue) times their associated probability value--> E(Net Contribution) = SUM(ContValue x P(ContValue)).  Thus, the question is why does SUM(ContValue x P(ContValue)) = $500,000E(Q) - $200,000?