Cloud servers have cheaper electricity, the scale of industrial-level cooling, no issues for you (as a user) with hardware failure (ie you just use a different server; it's not your problem) and can amortize their cost by running 24x7. I've seen H100 computer hours for as little as $2.

As the author notes, there are also electrical/wiring issues that cap how much compute gear you can run in a space not designed for it. I suspect a standard 20A 110V circuit can probably handle 2x RTX 6000 Pros. 15A probably can but that requires more research. Anything more than that and you're using multiple circuits, which has issues, or you need an upgraded circuit (eg 40A 240V) with all that entails (eg heavier duty cables, custom plug, etc).