What makes them so expensive is that they are the only 2 companies that make conversion kits for almost every make and model of car.
It's not cheap to have to design that many different conversion brackets. It's a lot of engineering resources, time, and work with the different auto manufacturers.
In short, yes the actual material you are paying for isn't worth the price. You're paying for research and development.
Now, if you just want cross bars when you already have rails.....that's a different story since you don't need any conversion parts that are specific for your car.