You are paying for your equity in opportunity cost. So, roughly, if you take your possible market salary minus your current salary over some time period, that's

You are paying for your equity in opportunity cost. So, roughly, if you take your possible market salary minus your current salary over some time period, that's what you're paying to purchase that equity. The straight financial calculation to make is - do you feel that that equity is worth that price - if you had that cash in hand, would you buy the equity with all its risk? This is one financial estimation, it isn't the only consideration, there is career experience, cashflow to support your life style (is the salary so low that your life is being impacted), etc to be considered too. However, if you don't believe in the equity, is the opportunity cost you're paying worth the stackup of everything else that's positive about your position?