Is it possible to recoup the investment by charging readers for the app?
Do account upgrades work? i.e. can App users buy an account upgrade and does it connect to paypal like it normally does?
Are there any additional costs related to the App?
If you have app store accounts, and you set up a merchant accounts on each, you should be able to charge for the app to recoup your costs with no issues.
Add paypal.com and
www.paypal.com to the add-on's domain whitelist so it can open in the app and yes account upgrades connect and work like normal.
Whitelist is what domains can open in-app. In 2.2, paypal will connect and open outside the app without modifying the whitelist (which is how it should work).
There are 3 plans: Turn-key (standard, we do the work and use our app store accounts), Enterprise (we do the work and use your app store accounts), and DIY.
(DIY means you do the work and use your store accounts, but it will be removed and replaced in 2.2 due to lack of popularity)
As mentioned earlier you need app store accounts to charge for the apps, and those carry their respective fees; you also need the TMA Enterprise plan which costs more.
There will be changes to make all plans (including Enterprise) more attainable in 2.2, so if you are interested, I recommend holding out until then.