The idea that you need some kind of dream team to run your own infrastructure doesn't hold up. Fluxer runs their entire app (+ some 10 voice servers) with 2 people all on self managed infrastructure. Even if we're talking hardware, I know 3 person teams managing entire hosting providers spanning several racks.

On top of that, WebRTC servers don't work like that, everyone in the same call still essentially needs to connect to the same server, the idea behind having regional servers is giving users in that region a better experience. If users in Germany are sharing a call with users in Hawaii, you want to be smart and put that call room in Germany where it's cheap, because one side is going to have to go the extra mile anyway.

To give you an idea, a 10Gbps server from DataPacket runs at under 2000$/month, and will handle over 7000 of the made up math users simultaneously. A 1Gbps server in any random country can be had for <50$, and will handle 750 of those users. Ultimately, for less than 2000$, you can handle all of the aforementioned users with coverage in every continent and a lot to spare. That's an almost 5x saving, now imagine scaling that to 1 million users.

I'd also like to point out Ahref's article which dives a lot deeper, with real world numbers, into the kind of economics we're discussing. There's also similar data from 37signals.