>I'm actually confused about why datacenters raise electric costs

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.