Before I comment on your OP, perhaps you might consider answering one question. Why did you start a thread that generates 7 pages of responses; but, only participate with one additional post? FWIW, that makes your OP appear to be trolling.
Anyhow...
The OP does pose a fair Q, which continues to be discussed on TB. There are a number of aspects to consider.
First, Econ 101 says that price is all about supply, demand, and specifications. Bass Guitar pricing is no different.
But, the OP goes one step further, asking what do higher priced instruments do that lower priced instruments do not. Fair enough.
The answer lies in understanding the range of gig requirements, for which players compete. There is a huge range of gigs! Thus a huge range of basses. It’s like picking the right set of clothes for the occasion.
Let’s take our upright brothers and sisters for just a moment. If one plays in a major symphony orchestra as a gig, the orchestra typically will prefer a VERY expensive, possibly 200+ year old instrument. Why? Generally for a combination of tonal and aesthetic reasons. Do 200 yo Italian basses necessarily sound better than high quality current production basses. Not to most critical ears; but, that’s the gig. Do the 200 yo Italian basses sound better than Kay plywood basses? To an untrained ear, I would say no; but, the player certainly can discriminate the differences.
Basically same thing for electric bass guitars. And, you have to understand that there is an entirely separate collector market overlaid on the older Fender instruments. So, no, in many cases price does not equate to instrument playing qualities.
Smaller builders, such as Alembic and Fodera as examples, charge what they need to charge to build their differentiated products and stay in business. The fact that they stay in business suggests that the demand exists. Do their tonal qualities appropriately scale from an MIM Fender bass? Clearly from a player perspective, the continued demand says yes. But, players both experience the instrument in a different way from a listener and are subject to different gig requirements. So, the average listener may not be able to differentiate the Alembic from the MIM Fender; whereas the player is just trying to hold down the competitive gig and sound as good as they can.
To address your own Q, I would suggest that you go out and try to play an Alembic Series I / II bass and an MIM Fender through the same rig and come to your own conclusions. When in doubt, try the extremes. I expect you would readily experience the differences. Whether or not those differences are important to your listeners depends entirely on your gig.
And, then there is all the stuff in the middle.
Hope that TL;DR answer addresses your Q.
