The problem is that doing it costs $15,000, minimum. So even at $10/person, you need 1500 paying people to break even. I don't think that's happened yet.
Plus, the second you take money for it, then you actually have to deliver. When it's free, and it cuts out for an hour or two, no biggie. When somebody paid for it and it cuts out for an hour - or their computer or internet connection or whatever just sucks - then you've got the whole customer service problem.
There's a reason there's pretty much *NOTHING* on the internet that is both live and fee based. Live? Yes. Fee based? Yes. But not both. Nobody has figure out how to reliably deliver live content yet. Nobody has even figured out how to reliably tell if you're reliably feeding live content - so at least then you could auto-refund the people who didn't get what they paid for.