Buy Micron 32GB DDR4-3200 ECC UDIMM 2Rx8 CL22 MTA18ASF4G72AZ-3G2R. FREE US Delivery, guaranteed 100% compatibility when ordering using our online tools.
A the bottom of the page there is a discount of 10% on the first order if you join their mailing list.
Looks like a good deal for NAS / Workstation system that use desktop CPUs.
Just over $2/gb delivered.