I'm speaking from experience and inside knowledge of the logistics of delivering home Internet service.
If a sample of, say, 95000 users doesn't get anywhere near a 250 GB cap, then that's a pretty good sample to say this behavior isn't common. Also most ISP's allow you to get higher caps with higher service plans, so if you're going to be that heavy of a user, you should pay for it. We have corporations running servers on their connection that don't go over 100GB a month.
Profit margins on residential Internet is razor thin (I'm talking like a couple of bucks profit per customer). The infrastructure of supply cable or DSL is most likely already paid for, but the OC-48's and other connections to backbone providers like Oarnet, Level 3, and such are insanely expensive. This is why they bundle Internet with more profitable services. Once you start using over 100-150GB, those profit margins dry up, and going over 200GB means they start losing a lot of money. Businesses need to pay their workers, and therefore you have caps.
I'm not trying to be a jerk, a know-it-all, or belittle anyone that uses a lot of bandwidth every month, I'm just trying to give some idea what it's like from your ISP's point of view. Extreme users are honestly not all that common, and they tend to congregate in tech forums (like this place!).