i've got examples too.
I needed custom 15x10 wheels for auto-x. Bought steel wheels $150 each, but they weighed more than I wanted. After a few seasons, i found some aluminum wheels $300. So bought the more expensive aluminum wheels, and took a hit (-$100) on selling the steel wheels. Shoulda just bought the light aluminum wheels ($600 total) in the first place instead of $800 the cheap way.
another case, bought an ebay bolt adapter spacer for like 70$. cracked them after a few events, ended up having to get custom spacers made. Only cost $100 because a buddy is a machinest. So spent 170$ the cheap way, instead of $100 the expensive way.
however, being cheap has taught me how to do alot. I can swap suspensions, do my own alignments, change clutches, all regular maintenance, rebuild and install supercharger.
I've saved many thousands by getting my own hands dirty.
May 2014 ROTM, June 2015 ROTM
for auto-x: '04 Liquid Grey ZX3
for street: '02 Infrared SVT