Primarily the feedback loop of cable companies "having to" carry ESPN/ESPN2/etc at vastly higher rates than any other network on television, resulting in the ability to bid up TV rights for all major sporting events. As long as the rights are expensive, the network will be expensive, and vice versa.

I generally enjoy sports, but don't care about the endless commentary and talk shows that populate ESPN 24/7, nor do I like the fact that their properties drive up everyone's cable bill by $20-$30 per month, an order of magnitude more than any other network.

It's one of the primary reasons I don't have pay TV; I wish I could allocate my pay TV dollars to the programming I find more valuable.