The opportunity cost is a big deal, and will gnaw at you the longer you're bootstrapping (+ consulting, which is typical) without making up the difference with sale of the company or an even bigger salary.
As tech salaries have ballooned in the last few years, the opportunity cost has gone out of whack -- if you go read message boards of what people are making at FAANGs, the odds are stacked against the startup founder / bootstrapper living on ramen for 5 years because the FAANG salary makes millionaires with 100% probability.
For any 5 year startup to make up for that it most likely needs to exit at 30M or greater which puts the founder in top 2% territory.