[ Update: I wrote a long post trying to explain some of what it takes to keep Simplify running and why a one-time payment wouldn't keep the lights on: https://on.simpl.fyi/p/complexity-of-simplify ]

That was actually my original plan. But the price range was between $2 and $5 as below $2, with my current user base, I started to worry I would not cover my costs. This is because:

a) There is a fair bit of research showing that the difference between $0 and $0.01 is larger than the difference between $0.01 and $X. This is to say getting people to pay anything is really hard. Several people with experience converting free products into paid told me that anything above 5% conversion was really really good.

b) Realize that there are sizable fees on every transaction -- I do not get the full $2.

While some were happy to pay $5 / month (feeling they got that much value out of it), I got a lot of pushback on the pick your own price plan with people saying it was confusing (which I agreed with). So I decided to bet on a lot of people converting and just made it $2 for everyone.