Good luck with that if you have a non-technical user base. Gaining trust when the first thing they see is a big warning telling them this software shouldn't be trusted will also be really tough.
If it's important to you for users to trust your app, then there are ways to do that. One of those ways is paying the $100. There are other ways outside of that, though.
And it should be tough. The hurdle needs to be high enough to frustrate malicious actors getting people to run random executables they downloaded from the Internet.
A developer who doesn't want to put any effort into gaining trust doesn't sound like someone I should allow to run non-sandboxed code on my machine anyway.
:)
To reiterate: You don't have to notarize, if your users trust you enough to manually allow your app to run.