It's not like these things are cheap, and plenty of developers wouldn't have a shot of successfully delivering an app without the infrastructure in place to support them.
It should come as a surprise to absolutely nobody that the vendor wants their cut.
If we are having an honest conversation about who gets a cut of what, we have to realise that web apps still have bills to pay and people getting their cut of something — credit card handlers, payments systems, web hosting (and that ain't cheap, especially when demand rises) on top of the cost of hosting an API and databases, and plenty of other costs.