The beefy workstation cards are 2 slots, but yeah the 4090 cards are usually 3.something slots, which is ridiculous. The few dual slot ones are water cooled.
I find it challenging to get my 4090s to consume more than 300 watts. There are also a lot of articles, benchmarks, etc around showing you can dramatically limit power while reducing perf by insignificant mounts (single digit %).
so you are getting a better practical card for the price
if you are making a mining type rig, then yeah, the extra price is wasting money.
but if you wanted to build a normal machine, the workstation cards are the most reasonable choice for anything more than 2 gpus