I'm not sure post-spending is the right thing to look at. One of the many reasons working at a startup is an awkward sell is that it means giving up money during your lowest-earning years in hope of getting more in your higher-earning years. That's the opposite of the smoothing function a rational person would prefer. That extra spending may well have provided a large amount of extra utility.

As far as taxes, a big difference you didn't mention is that startups most frequently exit in a single liquidity event that can't be deferred (i.e. acquisition). Getting that $1MM in one tax year is much worse than spreading it out over even 3-5. At least in my locality, the difference between taxes on a $1mm windfall in one tax year vs. a senior dev salary at a place like Google is ~5%.