In my opinion, what makes
some Alembics super expensive is the content that people who originally order them put on them. It is not hard to add anywhere from 30 - 150% of the base price of an instrument when piling on custom features.
Alembic charges a lot more for special wood choices than most builders. That's just a fact of life. If people don't like that, the answer is fairly simple....don't specify special woods.
Alembic has a ton of body styles and more headstock choices than any other builder I have ever encountered. Nine different headstocks that I can think of off the top of my head. I'm sure I am missing some.
Their electronics are varied, unique, and (in my opinion) unmatched. They manufacture all their own electronic components and pickups. For that matter, Alembic manufacturers all parts of their basses EXCEPT tuning pegs.
Buyers can mix and match not only wood types, but body styles, headstock styles. And then there are the more frivolous options. Both my current Alembics have side LEDs. Some custom orders have absolutely crazy inlays. The craftsmen at Alembic hand (including the owning family) hand make the inlays.
Look at the inlay on the bass the gave Stanley Clarke....the only bass they've ever GIVEN to an artist. Which partially answers the " if they are so great why don't more artists play them?" question. You'd probably be surprised at how many bassists who play endorsed basses on stage have an Alembic they paid for in their home. Some, like Stanley, buy and play Alembics.
And every Series I and Series II instrument these days (since 2005 or so ) get this cool headstock inlay, unless they ask for (and pay for) something a little more special....
No doubt, Alembics aren't everybody's cup o' tea, but enough of us do appreciate them enough to keep them in business.
Hopefully I've done a little to explain why they cost so much and why so many of us think they are worth it.