Why though? People who are price insensitive enough to pay 120 bucks a year for a menu bar widget are not your target audience, they are a tiny tiny minority.

They might be a minority. They might be a minority you're not in. So (I'm guessing) is the minority that buy genuine Louis Vuitton handbags. The question isn't the size of the market in total audience numbers, or the proportion of some arbitrary population they represent, it's the readiness with which they can be parted with a sizeable chunk of cash in aggregate.

Proving that the total addressable wallet is sufficient to sustain a YC company is a) non-trivial, and b) their problem. If there's one thing I've learned, it's that there can be remarkably large markets in remarkably unexpected places, so while yes, this one looks like a totally conventional small-software-shop play, and the 75th percentile outcome across all YC companies is crater-shaped, I'm not going to second-guess whether they might have something.