If you develop an app based on this network of contractors, how can you be sure they'll always be around to support your app? Do you make a local copy of the foreign app? What if they increase their fees and hold you up for ransom?
And you don't need to worry about suppliers increasing their fees and holding you ransom... again, that represents demand: another enterprising developer can come in and fill your need for a more reasonably priced service and undercut the exorbitantly priced supplier (who will likely go out of business quick-smart).