Back in January of 2007, I bought a seven-year-old Trek 1000 for $100. It needed a little work. I decided I liked it, and got it new wheels too. A year ago, we tangled with a Pontiac. Liberty Mutual bought it a nice carbon fork, new headset and stem.
All that remains of the original $100 bike are the frame, the handlebars, and the bottle cage bolts. Everything else--right down to the little plastic cable guide under the bottom bracket--has been replaced. And in many cases, upgraded.
Thank heavens I still love the bike and ride it regularly.