> But by and large the problem is that the anchor price for the browser and browser extensions is $0.
Great point. This was my thought initially which is why I suggested my friend to try a donation/pay-what-you-want model [1] before even trying to charge money for it outright. This might give an indication of whether the app solves a pain point enough to make people pay for it.
[1] https://www.emailthis.me/pages/support-email-this-donation