The prior is the market. It isn't sane to use your own prior experience. (Works both ways -- if your last startup did great, shouldn't assume next will).
> 4% of YC companies become unicorns. How many startups do you need to work for before you become part of the 4%? That number is not a feasible number of jobs for one lifetime.
The bar (and what the model is calculating) is Series A from top VC, not YC Seed funding. That significantly increases odds. Specifically, ~45% YC companies get Series A, so it's more like 10% chance of a YC Series A funded company becoming a unicorn (https://www.lennysnewsletter.com/p/pulling-back-the-curtain-...).
Model is change jobs every 18 months if not booming. A 1 in 10 chance is quite reasonable over a career.
I agree there is an issue with the event being too rare, but you can't just look only at modal returns. 2/3 chance of $0 (the modal return) and 1/3 chance of $10 million profit is still pretty good odds to work with.