I don't quite understand the chart- do they count the number of people online at peak time, and the result is the no.shown in the chart?

If so, the actual playerbase size is multiple times that. In XI's case most servers had an active population of about 20k people, simultaneously online being around 2500~3500 at time. It came down to around ~300k total players a while ago.

i would be surprised if the current playerbase is as much as 100k, but considering these numbers it's actually realistic. Quite high, but most likely drops to ~50k soon enough. That's pretty much what I had assumed.

If those 50k people pay for the upkeep fees (not the developer/development fees.....) Then it was a worthwhile thing to do. Can't see why it wouldn't.