Tor is configurable bandwidth wise. If I wanted to saturate my connection 24x7 using Tor, I probably could. It isn't interactive use, so I don't have a problem with prohibiting that.
I run a tor relay-only node and have it configured to use a very modest amount of bandwidth, and I've never gotten a complaint from my ISP about it. I'm sure if I ran it 24x7 at 90% of my capacity, I would hear about it.
I do think we need to move to a better pricing model for internet access. Paying for unlimited that isn't unlimited just leads to endless arguments. The contract should be based on usage with some kind of measurement attached, and then you get what you pay for. The rate should be regulated, since right now US ISPs are near-monopolies.
My electricity supplier doesn't care if I run a datacenter in my basement, as long as I pay my bills on time. That is because I don't pay for "unlimited" electricity. If electricity would be billed at a flat rate then you'd have the eco police doing random inspections for incandescent lightbulbs, insufficiently insulated windows, termostats set too high/low, and so on. Better to just let people pay for what they use and they then have incentive to buy bulbs that don't waste power.