I've had some really cheap, but functionally perfect bikes, but since I started figuring out what I like, I've spent exponentially more money on my current bikes.
Starting with cheap:
KHS Montana Trail - Free hand-me-down
Bridgestone MB-4 - $40. I used this to commute on for a couple of years, without any big problems and actually enjoyed it, proving you don't need an expensive bike to buy into cycling.
Current bikes:
Mondia Special - $900. My first frame up build. It was kind of expensive because I had to learn/re-buy parts to figure out what's compatible.
Soma Saga - Touring/Commuter. This was my money is (almost) no object bike, but it fits great and I think I will have it forever. $1,500
Surly Big Dummy - Grocery hauler/Commuter. Post-deployment present to myself, pre-MMM, but I'm still glad I bought it. $3,000 with all the accessories.
I check my bike mileage occasionally and make a game out of miles biked vs miles driven. Given $0.32 cost of driving my car per mile, I've saved about $950, this year so far. I'm trying to get to the point that my bikes essentially have "paid themselves off". I know it's not a real number to go by, since I don't plan on selling my car, but it's fun to think about.
Attached is a picture of my Surly Big Dummy carrying a full cart's worth of groceries. There's 2 watermelons, gallon of milk, 2 liter sodas, among other things you can't see in this picture.
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