In my experience, part of the cost of a better bass is due to selection or customization of elements that better match the needs of a given player.
I don't play expensive basses, but I have customized a few of the basses I already own to make them more comfortable to play for extended perods of time, to make adjustments for playability faster or easier to achieve, to replace tuning machines so the instrument stays in tune better during gigs, to replace one kind of fret with another, to enhance an instrument's balance or reduce its weight, to modify the sound, to replace the controls, or to improve the looks. If I weren't capable of doing the work myself, I would likely have chosen between a different instrument that already had the attibutes I was looking for, or having a luthier do the customization. I wouldn't have bothered if the instrument didn't sound acceptable to begin with. None of this has much to do with trying to "look the part."
I read posts on TB all the time about folks buying an affordable instrument and making some of the changes I mentioned, above, all of the time. Somehow, the pro players I've known, who are on the road at least half the year, seldom have the time, energy, or requisite skills to make these kinds of changes themselves. Some have had the luxury of having some of the easier changes performed by a "guitar tech" who travels with the band. But most have done so by selecting instruments that already have the features they are looking for, which typically cost more. The touring pros I've known spend more time strapped to their instruments than the bassists on TB. They typically want their instrument to give them what they want, consistently, gig after gig; touring and recording already gives them abundant challenges without having to worry about their instruments.