Does T-Mobile actually extort companies for transit? When they announced their video streaming throttling + zero-rating, I looked through their the publicly available documents. From what I recall, there wasn't any sort of payment process, and mostly there was two parts: identifying the traffic so T-Mobile knew to zero rate it, and either adaptive bandwidth usage (which seems pretty common for video streaming anyway) or identifying the traffic so the provider could serve lower bandwidth streams.
It's not in line with the net neutrality, but it's useful for the direct parties:
a) a video streaming customer wins because they can do video streaming without touching their data allotment.
b) the video streaming server wins because their customers are able to do more streaming
c) t-mobile wins because they've reduced bandwidth requirements
Competitive streaming services that are not included in the program don't win, but t-mobile made it fairly easy to join. Users who want to stream at 4k or whatever don't win, but they can turn off the bandwidth restrictions and use their data allotment if that's what they want to do.
At my last job, I was involved with a lot of zero-rating deals as the application provider; we never paid for it, and I don't recall ever being asked for payment. Some of the carriers even setup plans without our knowledge or consent or assistance; this didn't usually work great long term, because of misidentified traffic, but it indicates the demand was there without us pushing it.