Similar thought, and Google acquire does seem like a plausible route. However, checking over on Play [1] they've apparently got In-App purchasing at $3-50 and 300+ cities and 1000+ transits that let you buy fare and passes. Seems like they're already making money anyway. Teams pretty extensive though, so it does look like a lot of annual money's probably necessary to float. [2]
[1] https://play.google.com/store/apps/details?id=com.thetransit...
[2] https://transitapp.com/team