In 1990 I bought a Giant ATX 770 mountain bike that was a year old. I paid just over half it's price new. Was ~$500 at the time and was Giant's second best mountain bike.
I rode it to work and school for 2-3 years when the weather was cooperating. I rode it for the pleasure of riding it a lot. I rode it to the bar, and I rode it to and from the mechanic's shop when my beater car was getting fixed (~20 mile ride), and I rode it too and from the gym and rugby practice.
In 1996 I gave it to my brother to take to Colorado with him, in 2001 he gave it back to me, a bit more beat up, the red dust of the trails outside Carbondale on it still. I haven't washed it since, either.
2 sets of tires, 1 seat. I set of bar ends. I do need to get it tuned up because some gears skip and I would like to replace the handgrips.
I still ride the thing 3-4 times a week. Usually with my daughter on the back on a tagalong, but sometimes I'll go for a 6-10 mile ride as fast as I can make it.
My wife asks me if I want a new bike, and, honestly, I kind of do. I kind of want to get one with the bigger tires, and I kind of want one with a full suspension, and I sometimes think I can make my old one a fixie, and that would be cool.
But, fuck me, I've been riding this bike longer than both my marriages and longer than I've had kids.