3090 has the same VRAM amount, bus width and similar throughput, which are important for machine learning. It is about ~30% slower than a 4090 (this changes depending on the application) but can be had for a a third of the price. I just got one from the hardwareswap Discord for $660.

I still play in 1080p 60Hz

At some point I will move to at least 2k, although still I’m not bought into 4k as any perceivable benefit.

1080p is 2k. It's 1920x1080. 4k is 3840x2160. It's four 1080p screens, essentially. Maybe you mean 1440p as your stopgap in between? Not trying to be a dick, just trying to help. But I do think that if you were choosing between upgrading to 90-144Hz framerate and upgrading to 4k resolution, you're right that the resolution difference doesn't make much sense, unless you're sitting close to a large screen. You'd probably see more of a difference in raising other graphics settings like antialiasing or qualities of shadows and reflections. Raytracing blows my fucking mind, and as engines get better at light diffusion, it's gonna get harder to even imagine what better graphics could possibly look like.

Cheers and good luck!

If you just need more VRAM, AMD is your best bet. The 7900 xtx has 24gb and performs in between a 4080 and 4090. For $200 less than the 4080.