$0. Because it is an interconnect agreement. There is no prioritizing.
Although the deal doesn't technically violate net neutrality, because it concerns peering with other networks, Comcast is absolutely prioritizing Netflix traffic through their policy of paid direct interconnection with Netflix. Packets delivered by non-paying entities like Cogent are being throttled by Comcast refusing to upgrade their peering ports.
In effect, there are already fast and slow lanes on the internet.
What Riot needs is to put servers somewhere other than Portland, one of the stupidest places they could possibly put servers.
Portland is quite an excellent place to put servers. Cheap green power, plentiful IT talent, and direct fiber access to almost every tier 1 ISP. Many companies have servers in or near Portland, including Google, Facebook, Apple, Intel, Amazon ...
The thing is, when Riot decided to pick Portland, they didn't know that Comcast and Verizon would try to kill settlement-free peering with said tier 1 ISPs.