And maybe this is antithetical to OSS, but what does a closed source design cost?

Efabless websites states 10k usd minimum

That's quite affordable tbh. I'll need to see how custom that lets you get

All masks including reram are fully controllable in around 10 square mm

I'm still learning the lingo, is that a high level of control?

That's like 100% of the control. The only missing piece is control of the packaging, but it might be even better

Okay cool. And what sort of complexity does 10s mm buy at the 130nm? Like is there a general idea of how many mm you'd need for like a 64bit core?

It really depends on the core. But two 32 bit, one 64 bit with cache should fit

I assume you mean like what features it has/pipelining stuff like that?

Yeah