You are using a VERY limited definition of boutique. Remember, all that boutique means in the technical sense is a relatively small batch producer that typically has the 'founder' directly involved in the manufacturing... resulting in, by definition (i.e., lack of economy of scale in production, purchasing and distribution), high prices/cost.
Regarding hits.... MANY of the relatively recent modern country and pop hits were recorded with Sadowsky basses, Lakland basses, Ken Smith basses, (and Fenders and Music Man basses, of course) etc. Boutique has NOTHING to do with a specific tone, but rather small batch, quality made instruments with more detail and emphasis put on construction, assembly, quality of components, set-up, etc.
If Stanley Clarke's Alembic tone (one of the worst IMO in the history of bass playing) is the first thing that comes to mind in a 'boutique' discussion, then we are talking about VERY different concepts here
Edit: To give Alembic, the 'father all all boutiques' its due after my snarky Stanley comment above, check out Jimmy Johnson's work with James Taylor. That has to be among the best recorded bass tones of all time to me, and it sounds just as good coming out of the mains in a live setting (check out James Taylor live.... THAT is a bass tone, and Jimmy's true front of house tone sounds very similar to that 'through the board live tone' on that wonderful disc.... IMO!).