You can still buy the Framework Strix Halo board (with 128GB RAM) for $2k. For now.

I have a 3090, yet I’m still seriously considering it. The CPU itself is an engineering marvel, not to speak of the ridiculously fast RAM and IGP.

Only caveat is you better be a Python/Linux person. As you will be building forks and beating your head against the screen to get the setup working right.