Why waste money on an expensive bass for a loud concert? You're not going to hear any difference between that $300 bass and a $12,000 Fodera in that environment. Even if you did, the player may prefer the sound of the cheap bass for his genre.
I think this is it right here. If you want to take a really expensive bass on tour that could get lost, stolen, or damaged well that is your business. The original post was about a fairly heavy band and as an audience member I don't think that you can tell the difference in sound at a loud rock show (though aesthetics are another thing). I play in a heavy band and there are effects that when I play myself are night and day different sounding but in the band setting you can't hear a difference (maybe a but of volume boost or cut). If I can't hear the difference between my some of my own effect being on and off how can the audience hear the subtle difference of one bass to another.
On the other hand, if you are at a jazz show or something else where you can hear subtle nuances then a better instrument probably can be heard.

