Ask HN: Experience with estimating WebSocket Costs?

I'm approaching completion of a Socket.io-based client for a popular game with no good existing digital options. I'm trying to learn what to expect for hosting costs on Heroku, Digital Ocean, or other alternatives for a websocket-based application and I'm having a hard time finding any real data or empirical comparison beyond their pricing pages.

Has anyone had experience with hosting websocket projects? What did it cost you and what platform(s) did you use?