1080ti

[Chick3nman]

It might be important to note that while you CAN buy many 1080Ti's for the price of a 4090, you can't actually run that many 1080Ti's without spending extra money on supporting hardware that isn't needed for a single 4090 or even a few 4090's. Just comparing the cost of the GPUs without comparing everything else necessary to run them is an incomplete cost comparison. With the 4090 being anywhere from 3 to 12x as fast depending on algorithm, it's also not easy to just blanket compare cards across generations like that. Also, perhaps important to understand is that the 1080Ti is a very old card at this point and expecting long term support for them is probably not an ideal thing to do. Driver EOL is not the only thing to consider, as the CUDA Toolkit also has it's own versioning problems and when it comes to getting older cards to work properly you are likely to be stuck on older versions that essentially phase those cards out first in terms of being "up to date" enough to be useful.

If you are cost optimizing a build, you should be buying from newer generations that the 10XX series in general, for more reasons than just raw "hashes per second per dollar" unless you have a specific algorithm you intend to run and you are looking only for that metric.

For some quick examples of why this isn't so easy:
4090 can do 240kH/s bcrypt, 1080Ti can do 20kH/s. 12x faster.
vs
4090 can do 285GH/s NTLM, 1080ti can do 51GH/s. 5.6x faster.

Comparing these cards requires a little bit more work to get accurate numbers.