Note that the Reagan administration negotiated “voluntary import quotas” with Japanese car manufacturers in the 1980s when US car manufacturers were being beaten by Japanese brands
Anecdotally, if you asked me to pay $30 up-front for a password manager, I would just keep using the same minimum-effort password for every site like I was doing a few years ago. Data-wise, we know that the largest drop-off during customer acquisition is when they have to input payment information.
IME most people don’t want to pay for anything at all. Which is partly why the subscription model works — try it for free for a month so you can understand the value proposition. Afterward, you’re more willing to pay for it.
My understanding is that the monoculture being discussed is macOS rather than Safari. I would be surprised if most developers tested UI primarily on Safari considering, like you said, most people are Chrome users.
Anecdotally, most engineers I know use Chrome on a MacBook. The only people I know who use Safari are my parents.