But what the ISP cannot do is artificially inflate their advantage, as doing so would be in violation of a free market on the Internet.
Can we please stop using this term, please? It's pretty clear that we can't agree on a definition of "free market"(¹), so we might as well stop using it.
(¹) For many people, the idea that one must restrict the ISP and subscriber's freedom of contract to preserve the free market is a logical contradiction.