If you haven't caught an audience yet then you're probably streaming to very few people. A few dollars can cover that bandwidth until you get one or two subs or donators.
I'd also venture to guess (no hard numbers) that most successful streamers -- measured as "they don't need a day job" -- started streaming as a hobby. Such a person is much more likely to be willing to spend a few dollars a month, especially considering they'll likely already have purchased a microphone and webcam.
That being said, maybe it's better for it to be free considering the people paying for such a hobby would be among this "massive pipeline of kids dreaming to be stars".
In practice there are lots of ways to stream for free to a small audience, and that is a good thing. I just don't think the idea of paying for bandwidth would be much of a barrier.
It's a good idea that just revitalizes the old agent-management-star relationship. I wonder if this is how they do it in Japan with their idols and such. I don't know of any single platform that they all market on, they all roll their own website and such and the agent/manager funds everything.
On the other hand, seeing it/knowing it from real life and seeing it now making anime as a standard plot is also exciting and a bit sad. See Aggretsuko and Oshi no Ko. Both are products of pop culture of Japan that reflect the current trends of this management/money first style.
That being said, maybe it's better for it to be free considering the people paying for such a hobby would be among this "massive pipeline of kids dreaming to be stars".