I've found the most satisfying way to feel rich without spending a lot of money: upgrade the CPU on older server class hardware.
Server CPUs fall off a cliff in value pretty quickly. Xeon E5-2699 v4, launched 2016, MSRP $4,115. I just ordered one for $100.
Xeon X5570, launched 2009, MSRP $2800. Two years ago I bought one for $4.