The cost estimator basically says the incremental cost is $0.27/hour. That's pretty expensive for what is, in this case, basically bare streaming infrastructure (livestream adds some value, but not much for this particular use case).
The essential functionality could be easily replicated on e.g. Amazon EC2 at less than half, maybe even 1/3rd, the incremental cost even as a one-off thing.
Even now, as a not-particularly-wealthy person, I'm often willing to pay extra for convenience, but I just don't see ever being willing to pay 3x the cost of doing it myself for a non-mission-critical application, especially when there are even cheaper options like twitch.