If your primary motivation is financial, you need to think carefully. You are taking an irrational and outsized risk as an early employee if cash compensation is below market. But people play negative expected value games all the time at the casino.
Even if the expected value of the equity is "above" market, the variance on that projected equity is significantly worse for you than getting it in cash.
Either way, you should push for roughly market cash compensation, framing it as "your expectations." I have said these exact words before: "The salary figure is definitely below my expectations (which is $___), I'm worried this won't work out." And then pause to get more information from them. Remember, your expectations are framed by your alternatives, which makes it easier to walk away. Best thing is to have another offer, if you don't it's not the end of the world though. They still have to fill the position, which is leverage for you.
What matters is how much added value you bring to the company. The difference between your value and your salary is (in some sense) the profit that the company makes on you.
Further, is it your assessment that the plausible value of the stock brings you in just above market rate, or your bossess? Even if they're right, why be happy getting a bit over market rate, if you think you could get more?
No you don't. You just have to know that cash today is always better than the potential of cash later.
Also, you can't pay rent or buy food with equity.