The real costs are externalised to society and the environment. I assume you weren’t including that in your “reasonable costs”.

Nobody really cares about externalized costs. If they did, then cars, electricity, lithium batteries, etc wouldn't be as popular as they are.

They really just need to mandate that new datacenter construction uses closed loop cooling, and must provide an upfront investment sufficient to add enough carbon free energy to the grid to power it. That would, of course, make it much more expensive, but maybe it'd be enough to make investors consider whether lighting trillions of dollars on fire is really the best use of their money.