The payment gateway stuff is a real pain, I'll give you that.

For the rest, your responsibilities don't really change. Either you're going to respond to your users (customers) and maintain the app, or you're not. That has nothing to do with money.

If you aren't planning on supporting an app, you should probably make that clear in the first place. Remember: Your users are investing their time in you, and to them that's worth at least as much as their money.