Multipler: what API to use? UNet HLAPI, Master Server, or Play Games / Game Center Real-Time Multiplayer?

We have done using Unity 5 UNet HLAPI making WIFI multiplayer in our mobile game, and now we want to implement for global multiplayer.

The easier way of course using the new Unity Multiplayer server, but currently it's only in beta and the cost is extremely high for us indie game developers (Our estimated cost is 2k+/month!!!)

Then, we are thinking to downgrade to use Unity Master Server, or just use Play Games/Game Center Real-Time Multiplayer.

What should we use, and I couldn't find any example of a launched game using Play Games/Game Center Real-Time Multiplayer, is there any?