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?
As people dive deeper into a hobby they have very particular desires. That means two things: (1) specialty parts with very low sales volumes, and (2) people are willing to pay extra to get exactly what they want. If I just want two wheels and a set of pedals and don’t really care about the details then I can grab any $200 bike from a department store. But if I want, say, a very particular drivetrain, carbon fiber parts to shave weight, maybe a specific suspension design, mounting points for niche accessories, etc., then I’m shopping for very specific items from boutique brands. That’s why a very small number of hardcore riders do crazy stuff like pay over $4k for a set of wheels.
You’ll see the same thing in other hobbies, too. I can’t imagine what some people spend on their gaming PCs.