You seem to be confusing the expected value of a startup with the value of one's equity. There is a reason that the vast majority of vested stock options go unexercised when employees leave companies.
Additionally, you are not factoring in liquidation preferences. Rhetorical question: what's 10% of $10 million when your investors put in $5 million and have a 2x liquidation preference?
Additionally, you are not factoring in liquidation preferences. Rhetorical question: what's 10% of $10 million when your investors put in $5 million and have a 2x liquidation preference?