And then forget you bought them. I go through my parts stash from time to time and it is like Christmas all over when I find something I forgot I purchased.
I bought all new door sill screws for both of my trucks from LMC for a similar ridiculous mark-up. Something like five years ago, still haven't installed any of them. Sometimes I buy parts with the sole intention of stashing them away in case I need them someday. Thinking logically about parts purchases is no fun, don't feel too bad.