electrical supply is not infinite. datacenters have high electrical demand. more demand + same supply = increase prices.
>Why doesn't the data center bear an extra cost for the added infrastructure?
the problem is that added infrastructure is not built instantaneously. it lags behind. so costs will be high until more supply-side infrastructure is in place.
i agree that there should be some sort of stipulation that when you build your mega datacenter that you also have to build out electrical infrastructure at the same time. but unfortunately, that is not how it is.
I totally get the general principle that not everything scales linearly like that. But, I also know very little about electricity generation, so I have no idea where the breakpoints are. (I would also guess that if the demand dips low enough, there could be a case where after decreasing costs for a while, costs actually start to rise again as there is some minimum infrastructure needed but fewer customers to bear the cost.)
I suppose you can reduce a lot of both good at bad things about the country to "because federalism".