I say yes and no. I will give you an example. For the last 17 years, my two main basses were a 1994 and a 1995 Ibanez SR 500 Soundgear basses. I still have them and they are great basses. ... A few weeks back I traded my Taylor acoustic guitar for an Ernie Ball Music Man bass. It is a Sterling 4H that probably cost around $1,500.00 brand new in 2005. As soon as I played that bass, it was night and day difference to my Ibanez basses. It is just as comfortable, it is very balanced, but there is so much more to this bass than my Ibanezes have. It is way more versatile as far as getting different sounds out of it, it has a more balanced sound in that I hear all of the frequencies on this bass much more clearer, while both of my Ibanez basses and this bass both have active pickups in them, these ones are far more superior and it shows. Prior to this, I never really noticed a big difference in high end basses as opposed to let's say your mid grade basses but now that I have compared these basses side by side, I really do see a difference. ...
First off, I agree that whether it is worth it or not is TOTALLY dependent on the person answering the question, what they want, and how much they are willing to spend to get it.
Jay's post intrigues me though, because I believe that it might be highlighting one aspect not talked about much on this subject. As you get more experienced, you listen differently, and you hear more nuances. Most of the things you begin to hear, the audience is totally oblivious to, and some of them will get lost in a band mix anyway.
But if you want "that" sound, and "this" bass gives it to you, you may feel that it's worth it... just to please yourself. And that's as it should be.

