If it doesn’t make sense at $100/year, your apps just don’t make enough to matter to your budget at all anyhow.
Maintaining the integrity of an app store is a very non-trivial task, and building an entry barrier in the form of developer fees is one way of doing it. Not saying this is the only solution or even a particularly good one, but every solution will have its share of unintended consequences and exploited armor chinks. Making dev accounts free for no-ads would be an interesting experiment, though. I'd support it for science!