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Actually, bicycle manufacturers can afford to use expensive carbon fiber, because they need very little of it.

Here's an interesting fact. Did you notice that you almost never see carbon fiber in cars? Even though it seems like a great product for automaking? Well, car manufacturers are very interested, and they are watching the industry closely, but it's still too expensive for mass-market cars and that's why it still only goes into exotics. You need 2-3 pounds of carbon fiber and epoxy to make a bicycle frame that sells somewhere on the order of $1000. With this cost-benefit ratio you can splurge on expensive stuff. An automaker wishing to make the body of a car completely out of CF instead of aluminum needs 500 pounds of raw materials, and he can't afford to raise the price by more than a few thousand bucks. In automaking, CF is simply not competitive with aluminum above $5/lb or so.

Commercial aircraft are closer to bikes than to cars in this respect though. It takes 80,000 lbs of carbon fiber and epoxy to build a 787 and the resulting aircraft costs $200 million ($2,500 per pound of composite materials).

You can buy a linear yard of 50" wide, 300 gsm "aerospace grade" (T700) carbon fiber (that works out to about 0.77 pounds) on eBay right now for $18+shipping.