Cloth components are very heavy and should be used very sparingly.
For any reasonable amount of vertices (up to ~200k vertices), a cloth component will add around 0.2 ms per 1000 vertices. Above this, the frame time shoots up hard before tapering off, but this is only with unreasonable amounts of vertices.
Note that this 200k vertices limit is for the entire lobby. The amount of cloth components does not seem to matter for the lag, just the amount of cloth vertices.
Note that due to mirror and shadow clones, the local avatar’s cloth is simulated three times, and therefore its vertices should be counted thrice
Colliders will make a cloth component take about twice as much frame time per 10 colliders. So per collider, it will take about 7% more frame time.