I have 2 bikes. 1 bought and then completely changed out. The only thing left is the frame and stock wheels. But I'm done with it, I want a different bike and in the process of figuring out what I want.
My MTB was built/customized from the frame up. I will posit, and I can provide proof, that you can build a very nice bike for under what it could cost from an LBS if you're patient and willing to shop around. It took me over a year to put together all the parts for my MTB. I shopped ebay, nashbar, Pricepoint, amazon, all the usual suspects. I have an unusual drivetrain (XO shifters, RD, XTR FD and crank with King headset and BB) but it works beautifully.
Anyway, why would one spend all that money on upgrades? Many reasons. My reason was that my partner didn't like the idea of me building up a new bike especially when I had just built up the MTB. His reasoning was that it would be so expensive. So I bought a stock bike and changed everything I didn't like, some for lighter weight, some for better shifting and performance, and others just because I like some bling. And the second reason for me was that I wanted a very nice hybrid commuter bike and there isn't one sold from the factory with everything I wanted. I might add that I really wanted to build a nicer bike and I was just trying to overcompensate by buying some really nice gear.
So, I'm off to building my next bike because n+1 always rules around my house
. My base this time will be a Lynskey Viale or Cooper CX. I'll be building that over the course of the next year so that I don't get that stink eye look from the better half, LOL.