Earlier quoted context omitted.
If a normal game sends 2mbps, then 20mbps would be 10 times as many objects.
That's what I'm asking, seems like this isn't a normal game, but what specifically about it makes the bandwidth requirement so high? I know RTSes send inputs instead of state, but that has its own drawbacks.
Let's assume these FPS games send 1mbps - 2mbps per-client (many send less, some send more) but it's a good range to start with.
Now increase the player count from 100 to 1000. The number of objects that needs to be sent from server to client also 10Xs, because you need to send state for each player visible to each client, so that client can actually see the other players moving around. The end result is bandwidth is now approximately 10X what it was before, or 10-20mbps.
To address your question around RTS and inputs. Game developers usually end up using state synchronization methods (sending the positions, rotations etc per-object) instead of relying on input based deterministic methods whatever player counts are high. My personal threshold is around 4 players.
This is the reason FPS games and other higher player count games usually send state instead of just inputs. Because if they were to rely on a deterministic simulation synchronized only by inputs like an RTS, the server would have to wait for input from the the most lagged player before it could step the server simulation forward, and with regular internet jitter, packet loss and so on, as the player count increases it becomes more and more likely that the game will hitch and stutter waiting for these inputs.
So the answer is, bandwidth sent per-client scales with the number of players in the game, and games with higher player counts tend to send state instead of just inputs for the reasons above.
cheers