Spent £100 on a CK headset… Only once mind, next one was £60!
Haven’t bothered with a CK since, £25 cartridge bearing headsets do almost as good a job, last plenty long enough, and you don’t feel so bad knocking em in with a block of wood and a rubber mallet!
Think the most frivolous expenditure for me personally though was a pair of M960 XTR cranks brand new back in 2003 (to go on the same bike as the £100 CK headset). Not having been anything more than an average rider at best, why did I get XTR? Well, just cos I was being a tart! Cost me £250 and realising that they were a waste of my time and money, I sold them for £180 a couple of months later and they got replaced with some LX I think which did just as good a job.
Owned 5 pairs of those 4ti eggbeaters by the way, but only cos I got them cheap off a contact in a race team, and I sold them on for some profit. Wouldn’t use them when they do no better job than the standard pedals that cost £50 and only weigh 100g more!
Learnt the lesson about talking to non biking people about bike parts prices a long while ago though. Telling them you fitted a ti BB is probably easier, as it’s “only £100 or so” and they wouldn’t know what it was anyway. You might justify £1000 on a new Full sus frame much easier than £100 on a ti BB, but to a non biking person all they hear is the money involved!