I was able to find 2 x 16GB DDR4 for $150...

Building a budget AM4 system for roughly $500 would be within the realm of reason. ($150 mobo, $100 cpu, $150 RAM, that leaves $100 for storage, still likely need power and case.)

https://www.amazon.com/Timetec-Premium-PC4-19200-Unbuffered-...

https://www.amazon.com/MSI-MAG-B550-TOMAHAWK-Motherboard/dp/...

For a server that's replacing a 12 year old system, you don't need DDR5 and other bleeding edge hardware.