Pay to listen is not a good way to bootstrap in my opinion.
With the momentum of nostr right now, I think you will beak-even by just making it easy to stream sats to you when using the service.
When nests becomes a huge success and you're looking for ways to monetize further think with value4value in mind. All spaces on twitter are not worth paying for or providing any value.
Maybe woth considering long term:
Paid flatrate plans
Sharing revenue with creators
Just my 2 cents