I'm doing just that (using a bike that costs a third as much), and I'm really happy to have saved like $1500. All you need is any decent bike ($200-$600), a bluetooth cadence and heart rate sensor ($70), plus their cheaper $20/mo app and you get most of the experience at a reasonable cost. I don't get the output number and can't compete on the leaderboard, but that's fine. If they keep supporting things non-Peloton bikes like this, I can see them making a ton of money. I wouldn't be surprised to see an entry level bike in the next year or two.

I personally love the music (classic rock and EDM for most of my classes) but that's personal preference, and haven't had any issue with video stream.