Away from my desktop atm, but before spam filtering I was seeing consumption grow week over week on my public strfry relay. To about 1Tb per 7-10 days. It was still just on a VM then. It's about a quarter of the bandwidth after I started rejecting notes with URLs. I've since migrated to a dedicated server with unmetered gigabit, for whenever the next wave of growth hits us.

The paid relay network throughput has always been pretty stable, it's a tiny relay by comparison.