Water is a finite, possibly scarce resource, and there are shortages in places in the US. If I lived in one of those places, I would sure as hell want some asshole filling his pool during a shortage to pay more than the rest of us pay for basic drinking water. Similarly, I would want companies that bottle that water up and sell it at a premium to pay more than everyone else.
Municipalities already limit outdoor water usage for exactly this reason. You can drink all the water you want but you can only use it outside to water your grass or fill your pool on odd or even days. Your analogy is saying that shouldn't be allowed, because internet.
It doesn't cost anything more to use it at maximum capacity than it does to just leave it on standby. (The end points MIGHT use a TINY bit more power, but we're talking on the order of cents per month for terrabytes/month of traffic; it's a rounding error.)
The ISPs already offer and charge accordingly for home, business and commercial accounts(all pay more for more volume & speed).