Every worker gets to do this, and it happens a lot in startups and big companies alike. Stocks and stock options are (varyingly) anchored to whole-company valua

Every worker gets to do this, and it happens a lot in startups and big companies alike. Stocks and stock options are (varyingly) anchored to whole-company valuation, and early / senior employees that produce more value will often get more stock because they comprise a greater share of the company's health. If your friend insists on paying you a low flat fee for doing highly lucrative work, your rational choice is to turn down the offer and find another employer, or even go at it on your own. Your friend's rational choice is to negotiate because the lost profits from you (and others) declining the offer is worth more than the profits he loses by paying you more. Regardless of that, a single transaction like this is often not sufficient to accurately determine the market value of your contribution. Market valuation happens in aggregate for this reason. A single irrational transaction like the one you described just represents a market inefficiency.