1. 100$ is a pocket change for many people. Depending where you live. I think it is enough of a barrier to force a thoughtful action. Also, to compare, cheapest certificates for signing windows software are like 450$/year. Microsoft has a hosted service now for $15/year, but that is still in beta. Both of those options are significantly more expensive than 99$/year Apple charges.
2. No, Apple does not deny randomly access to developer accounts. Also, this is quite besides the poin.
3. Code Signing has absolutely nothing to do with submitting your app to app store, or anything Apple has to approve of. Like, why even write about something you have no idea about?
4. True. Not sure how it is relevant.