I think there is a law of diminishing return when buying anything. It doesn't just apply to basses.
If you buy a $100 bass and compare it to a $500 bass, there will be HUGE differences between the two. But if you compare a $1500 bass to a $3000 bass, the differences will be much smaller. Yes, the more expensive one will be better (in most cases), but you are gaining far less for your cash outlay. The value proposition is far lower on the more expensive bass.
There is typically a tipping point at which you begin to gain very little for the extra money you lay down. I believe that point is between $1500-$2000 (new).
If you are a professional player, I'm sure you could easily tell the difference between a $5000 bass and a $2000 one. But most people can't. I have a Lakland Skyline 55-02 and I had the opportunity to play the US version at NAMM and could not tell any difference. Not in feel, tone, playability....nothing. They felt the same to my unskilled hands.
I'm an avid motorcyclist, and I often get a chuckle out of guys who spend THOUSANDS of dollars to get their bikes to weigh as little as possible. Replacing everything they can with carbon fiber. Then you ask them how many track days they have done, and they say, "none". Or they brag that making their bike lighter dropped 2 seconds off their lap time that a 13 year old kid on a little 250 2-stroke destroyed by 20 seconds.
There is some merit to owning something that is exclusive, or owning something because you appreciate the care and attention to detail that went into it's construction. That's the whole concept behind jewelry and expensive watches. A $10 Timex keeps EXCELLENT time. Much better than a $5000 Rolex. But the Rolex is....well....a Rolex. It's beautiful and exclusive. That's why people buy them.