Except most providers don't charge by time and demand (which would actually make sense), but by a fixed cap or fixed cost per byte. If the problem is congestion as you suggest, surely it would make more sense to charge different amounts based on time of day, length of session, etc?

Which would give Amazon more trouble? 1,000 TB spread out over a month, or 1,000 TB spread out over a day? Their current pricing model assumes both of these are equal, which they are plainly not.

Aside: Caps make the same mistake. If you have a 250GB cap, the ahem ISP charges the same whether you burn through that cap in a month or in a day.