If you've got the money and don't need it for something else, why not buy a gold-plated bike with it?

On performance items in general, when you start getting to the better stuff, you wind up paying a LOT more to get a little more. You'd expect more of a difference between a $1000 bike and a $100 bike than between a $10,000 bike and a $1,000 bike. True of cars, watches, cameras, lots of other stuff. It'll be closer to a custom-made item, made in a high-labor place instead of China, made by people that aren't going to bother if they don't get some good income off of it, etc.

A $4,000 bike is still way cheaper than any new car sold.