There are some brands of bicycles that can cost more than the down payment on a car. Why? Surely making a bike lightweight and reliable isn't so difficult that it warrants that price? Is it just the brand name or maybe it has to do with customization options?
Making a bike lightweight is not so hard. Making a bike lightweight and durable is. Top end bikes use high end materials and are engineered to very high standards. But if you just want to get from A Too B, a cheap bike will do just fine.