That seems silly to me; it neglects value of information from trying a startup.
You're not deciding between "do a startup for the rest of ever" versus "be an employee for the rest of ever". You could for instance do a startup for two years and then quit if you don't get VC funding.
See http://80000hours.org/blog/12-salary-or-startup-how-do-gooders-can-gain-more-from-risky-careers.
The expected value of risky careers like startups if often much higher than less risky careers. However, this is more than offset by peoples' risk-aversiveness due to diminishing marginal utility. But... if you're an effective altruist, the money you make doesn't have diminishing marginal value. So... it seems that risky careers like startups are a good choice, if you're trying to maximize your positive impact.
What do you guys think?