That’s what their docs say:

At an absolute minimum, Dendrite will expect 1GB RAM. For a comfortable day-to-day deployment which can participate in federated rooms for a number of local users, be prepared to assign 2-4 CPU cores and 8GB RAM — more if your user count increases.

That’s not accounting for Postgres.

I got that. What I mean is that you can easily have a tiny 256mb VPS for a bunch of static websites or even some WordPress and the official matrix servers would require you to easily double or triple the bill.