There's no pricing on the website that I can find.
Are you really saying that you spent years of work and $1m+ of your own money building something that you love but that has no income and no path to income?
A free app?
You're very articulate and the comments have been interesting to read, but it all feels a bit like these: https://en.wikipedia.org/wiki/Folly
You need to go to your existing users and tell them that from next Monday the price is $x.
Unless you're independently wealthy and quite happy to continue building your perfect app and giving it away for free forever. In which case, carry on.