So I'm running these "Kingston Technology 32GB 3200MHZ DDR4 ECC CL22 DIMM 2RX8 Micron E @ $167.91 each" (I'm pretty sure they are KSM32ED8/ME) that I got from Provantage back in 2021, alongside 32GB of Samsung M391A2K43BB1-CRC for a total of 96GB on my 5950X. What's nice is that I will then have a full complement of 4 each of ECC DDR4 32GB, 16GB, and 8GB modules, the 16GB and 8GB ones I can fill up my Threadripper 1950X with to give it 96GB.
$120 is a steal considering that it cost $350 earlier for me to get the Kingston version of this.
I originally did careful research to get Samsung B-die and Micron E-die for this stuff. So I was gonna ask about compatibility but I'm not sure how much it will matter. And then went on to never attempt to overclock any of this ECC memory. I still don't think I intend to. Attempting to overclock the memory, even though overclocking with ECC is supposed to be fun and rewarding, when all 4 slots are filled with the highest possible density, just seems like a questionable thing to do.
I'd wait longer but these prices are definitely near the bottom of the trough. Older memory tends to go back up in price. So I would want to bring this rig up to 128GB before the prices start to rise again...