My guess is "not as much as most folks seem to think"
Comparable 24gb vram 4xxx cards are also 1 slot bigger and many watts hungrier. If you want to be able to use a 800w PSU + 3 slots, and just need 24gb vram for say, running inference on a big diffusion model, then 3090 is still going to be your only option for a while.
They're pretty well priced right now, at $1k. If you need one, not much reason to wait, your time is probably worth more than saving a couple hundred bucks.
The 4090ti is rumoured to be 48GB [1], but who knows when that will release or how much it will cost. If you really need extra VRAM and don't mind longer inference, older used Tesla cards are an option. A used Tesla V100 32GB can be sometimes found on Ebay for 1500.
It appears as though the 4090 will be 24GB, but that card may also be almost $2k.
Used 3090s on eBay are $800 all day long. That price may drop a bit in the next week or so, but not much, as that 24GB of VRAM is the main draw for that over a 3080Ti.
