Personally, however, I would be more fluid than “constant dollars”. Some people need more cash, and others need less. There are definitely people who would say “I basically don’t want any cash, just get me health insurance and more lottery tickets” while others would say “Look, I would love to do this, but my family needs take home pay above this level”.
Letting employees trade off equity versus cash comp at their discretion via a formula seems fair to me. Anyone who reduces their salary is effectively reducing the amount of money needed for fundraising or time to needing funding (and vice versa, for more cash). For that reason, the trade off is also non-linear for the company: early dollars are worth a lot more than later dollars (though the price per share sort of reflects this). Said another way: if you had a $175k baseline salary, but let all employees also exchange $$s-for-shares at the current valuation up to some limit, you should probably do it! (Large company ESPPs are sort of this). Doing this exchange ahead of time is just more tax efficient than “first we pay you cash, then you buy shares from the company”.