It's entirely dependent on hardware. Most installations are either not GPU-accelerated or extremely over-provisioned. A good VDI instance usually costs at least as much as per user as the equivalent desktop PC, if someone started the project because it would be cheaper per user it's a recipe for disaster.

The install at the bank was a bunch of racks filled to the gills with NVIDIA Grid cards and high-end Xeons, and they had a setup in every region they did business in (you could get your instance migrated to another cluster if you had to be in another office to reduce latency, IIRC). It was super interesting to me because it was one of the few times I've seen VDI work right, leaving the only blocker to dev work being the crazy security policies.