Rewiring the house for 240V supply and spending $400+500 to refurbish a second-hand UPS to keep the 2500W rack running for 15 minutes?
And then there's the electricity costs of running a 2.5kW load, and then cooling costs associated with getting that much heat out of the house constantly. That's like a space heater and a half running constantly.
Again, not trying to normalize 2500W, most people don’t need that (and I don’t really either), but I do make good use of it.
As for “rewiring the house for 240V”, every house* in Canada and the US is delivered “split-phase” 240V (i.e. 240V with a centre tapped neutral, providing 120V between either end of the 240V phase and neutral or 240V from phase to phase), and many appliances are 240V (dryers, water heaters, stove/ranges/ovens, air conditioners). If you have a space free in your breaker panel, adding a 240V 30A circuit should cost less than $1k if you pay an electrician, and can be DIY’d for like $150 max unless you have an ancient panel that requires rare/specialty breakers or the run is very long. It’s far from the most expensive part of a homelab unless you’re running literally just a raspberry pi or something.
*barring an incredibly small exceptional percentage