That's by far the cheapest part of it, decoding will eat more power and transistors than just few differential lines. Add few magnitues if you need to generate it in a video game
Differential transceivers and high speed circuit design is not cheap before economy of scale kicks in for that particular unit, but the mention of throughput was not as much to denote the link as much as to denote the speed at which content must render, scan out and decode...
