Roughly speaking we're seeing Jitsi serve around 1000 concurrent streams (i.e. 25x 50-user conferences) on a typical 4 core box with 8GB of RAM. However, it's worth noting that Jitsi is pretty low resource - all it's doing is forwarding streams of data around the place. All the heavy lifting is done by the clients when displaying all the concurrent videos, so it's the clients which tend to be the bottleneck.
