"You rarely get any help from others watching as the traffic simply isn't there"
If the traffic isn't there, your bandwidth costs will be low anyway? The idea of the p2p is to help if traffic appears, isn't it?
About the costs, I run a PeerTube instance and a Masto instance and monthly fees are broadly similar, at least in my case.
" it is being deprecated."
Is there somewhere with info about this?