What do you mean the subscribers do not produce revenue? Each user was generating $2.80/yr. in 2007-2008 fiscal year, based on the previous growth it has been projected for each user to generate $10 - $20/yr.
Worst case scenerio as follows:
5bil OS, although reported they were at 2.8bil but just for arguments sake.
$10 per user per year * 1.9mil users / 5bil OS = .0038