My anecdata: bought used DDR4 ECC 16gb ram sticks (i.e. serverpulled ram) for $11 off ebay last year (Jan 2025), now as of June 2026 the lowest listing I see is $42, most are around $50.

When I bought the same ECC DDR4 16gb ram stick in 2016 (when DDR4 was rather new) it cost $85 (cant remember if it was new or used)

To be fair, DDR3 is still kinda cheap. It's really only DDR4 and DDR5 that are massively in demand. DDR3 is a bit too old for it to be in high demand by consumers.