I thinks it's very reasonable. They provide an important security service, also the windows equivalent is many hundreds of dollars per year, per application, vs $99 per year which would cover any number of applications.
Quoting the last line of my comment again with added emphasis in case it was confusing:
> I'm not sure it is reasonable *to demand that open source devs pay a fee to Apple* so that you don't have to right-click the app and whitelist it...
Also, how does paying $99 mean that Apple “knows who you are”? It identifies you as somebody willing to spend $99, nothing more. I bet that’s not a problem at all for many bad actors.