LowT wouldn't do a damn thing except for pity post and chug wine if Jeffrey stole the forums.
The multiple terabytes of data thing was addressed over and over on SA. I don't know how true it it. Basically the forum is a holdover from much earlier tech. It can't run on a VM, or VMs and it doesn't do anything fancy like caching. Every page refresh sends the user a shit ton of data. It was the norm back in the day, which made hosting forums a lot more expensive than now. Somehow special cells and other junk really impact this in some way (FYAD, probated posts etc). It's a monstrous contraption incapable of being optimized without starting from scratch.
Or, more likely, there's 3 gigabytes of user data and the rest is because mods are trading CP thru messaging.