I would b interested to know that, too, at least a rough estimation. It's a pity that apparently devs aren't active here in thread, quite a lot of questions had accumulated.
Nothing what could be easy told, even by devs in my opinion. So many factors are important for this. In the opening post they wrote something about 2000$ a year. Well, it can be like this, it can be much more less.
can you imagine what sort of information is google getting about us? form search, email, maps, etc. try looking at https://privacy.google.com/your-data.html and I think it can be much more than 2000$ !!