When you can buy something at a low price in one location, and sell it at a higher price somewhere else, you’re engaged in what economists call “arbitrage”. We’re not sure if desoldering DDR5 chips from laptop SO-DIMMs to populate a custom PCB to create much-more-expensive desktop memory counts as arbitrage, but it certainly counts as a hack. [VIK-on], who built the cards, claims he’s getting DDR5 performance at almost DDR3 prices. Nice!

[VIK-on] is in Russia, so SO-DIMM rates may differ in your local market, but he claims walkaway costs of 17,015 ₽ — about $218 or €188, an astounding price for DDR5 in these dark days.
Some say soldering SIMMs seems severe, but hardly strange to Hackaday, and desperate times call for desperate measures. It’s ether that or optimize software, and who wants go to that effort?

“however: the part where we wish we had more details was in the firmware.”
It’s not ‘firmware.’ It’s the SPD EEPROM, the thing that tells the system what the various memory timing parameters are. The parameters are all standardized, but it sounds like he just dumped the EEPROM from one DIMM and programmed this one (or… just moved it over).