It looks like you can configure the Dell Precision 7920 [1] and the HP Z8 [2] both with 3TB if you want (admittedly at an absolutely bonkers price point).

[1] https://www.dell.com/en-us/work/shop/workstations-isv-certif...

[2] https://store.hp.com/us/en/pdp/hp-z8-g4-workstation-customiz...

More bonkers than what Apple is charging?

Yes, Dell actually wants a little bit more for RAM than Apple does. Not by much though.

I don't know what you saw on heir websites but we have an EPYC powered HP workstation with 1tb of RAM in the office for almost a year now.