It is more like the inverse. The big benefit is that as a user, you are able to acquire apps not distributed through the official app store. This can be useful for things like F-Droid.
For an app seller that needs revenue, the Play Store is the only practical option. Otherwise, they'd have to convince the user to tap the screen a half dozen more times, and that is too big of an ask. It'd ultimately hurt revenue more than the 30% tax.
Yes, but if you do use Google's store, you have to use their payments system (which is roughly 10 times the price of normal online payments processing).
Except if you're too big for them to lose your business since it would make their store look bad as a platform, or too small for them to bother, or they are distracted by some other shiny trinket on that particular day.
For an app seller that needs revenue, the Play Store is the only practical option. Otherwise, they'd have to convince the user to tap the screen a half dozen more times, and that is too big of an ask. It'd ultimately hurt revenue more than the 30% tax.