I think ISPs like segmented pricing models. Segmented pricing models let them extract more profits from sections of the market that can afford more. But segmentation by bandwidth cap doesn't seem to be very successful.
> Charging someone who streams 100 GB/month from Netflix more than someone who streams 100 GB/month from Redbox or Hulu is not.
Just to get some reality into these figures; on a 5Mbit line, 300G/month was typical for our house. Now that we have an 80Mbit line, I would expect our home usage is now well in excess of 1T/month. (I live in the UK.) This should tell you that I have no self-interest in bandwidth caps, especially joke 2-figure ones.
Given that, I agree that there shouldn't, in principle, be a distinction between packets from company A vs company B. But without being able to efficiently price the scarce resource via bandwidth caps and segmented pricing models on the consumer side, the ISP is reduced to negotiating with the upstream providers of packets that are consuming the scarce resource on behalf of their customers. It then becomes a business negotiation problem, with contracts, leverage and relative power. So naturally there will be variance in which company pays what.
Somebody has got to pay for the scarce resources being exhasuted. That person will be the consumer who downloads more. The only question is how the payment will be routed.