I don't think the fans of boutique basses are arguing that they're basically expensive status symbols; functionally inferior to their mass-produced counterparts; and appeal largely to hair-chested cheeseballs with more money than taste

Instead, let's say Patek Philippe and Porsche
I liked where you were going but the Porsche and PP argument still falls into your trap - a PP still doesn't *really* tell time better than a Timex, even though it's a work of art and a labor of love.
The better analogy for me is comparing things across the *same* high performance dimension - say comparing race cars to race cars, or high performance cycles, skis, etc.
Here's my point; if you buy a $50 road bike and take it to a race, you are probably going to lose no matter how skilled you are. As you spend more and more money the performance gets better in a fairly linear relationship to money - up to a certain point - lets say, around $2000. At that point, you have a good bike that performs really well.
However, as you push for more incremental improvements, the price tag starts to jump fast - even though the performance aspect improves more slowly. The difference in quality and performance between a $4000 bike and a $2000 bike is much smaller than the difference between the $2000 bike and the $50 bike. The difference between a $10,000 bike and a $4,000 bike is even smaller.
So I guess a $10,000 or $20,000 bike isn't worth it? Well.... Hold the phone. If you are at a level where every little bit of performance matters, and you are competing for a big prize - well then yeah, it's probably worth it. You accept the fundamental truth that to squeeze that extra performance out of the device starts to cost a lot, but it's worth it to you to pay up.
Sure, instruments aren't used in a race with a definite winner and loser - but the point is this:
For those that Foderas speak to, they remain expensive, but those folks have found that that's the price they must pay for all the little details and craftsmanship and attention that makes the instrument completely perfect for their needs.
If those aren't the things you are willing to put such a high price tag onto for a bass, peace. I would never buy a $10,000 bike or $10,000 skis or etc, etc, etc. But I would also never second guess someone that did. That person is someone who has said; "for this one thing in my life I will accept no compromise and I will buy the one that speaks to me regardless of the price because in this corner of my life its simply worth it to me".
Nothing wrong with that.