Sorry, you cannot use services like this within App Inventor. You cannot use Ad Mobile either.
To use other services payment options, you might migrate to one of the third party app inventor like compilers designed for commercial app development. Try one of these
https://groups.google.com/forum/#!topic/ai4a/ajG4Q6UrRR8 . Which one? You will have to do your own research. Once you change development platforms, stay with the new one. Backward compatibility is probably not possible.
Sorry, there is no free lunch. If you want to sell your app, you pay a commission unless you sell yourself (see below). If your app is popular and useful, paying the commission should be worth it. Consider, you do not pay for your development software. Is it worth it? Consider 60-70% profit is significantly better then 0 percent by not selling from a platform where your customers can find your app.
Alternatively, sell your app directly from your own Web site/server. This process is complex. It will cost you to maintain your server or host your WebPage. You will service the accounts., that uses your time. Advertise somewhere that your app is available (a Web Page? - design and maintain the WebPage) , arrange your own payment software (or buy one to use on your Web page). Collect and pay your taxes and ensure your app downloads properly to customers. Do you really want to do all that?
Regards,
Steve