Ken I understand
exactly what you mean about playability, fit & finish, etc. It's just that I have seen dozens of clips where folks are going on over the tone, and I just say to myself that it sounds like Fender.
Umm, that's my point

. For example, that Fodera NYC clip that you dug a few days ago sounds NOTHING like a Fender J to me. And, that clip really represented the tone of that bass well, based on all the ones I've played. It was a great tone which I didn't dig at all.
IMO, there are VERY few (using your example) boutique J's that sound like a Fender, and it's nice to have help knowing which one's they are (or which one's they are not, since some guys love the LOOK of a Fender, but really want a more 'modern' tone and voicing. So, it's also cool to hear the LEJ's, the Sadowsky's, the Fodera NYC's, etc. to gauge the general tone prior to potentially ordering one up.
Again, using the boutique J thing as an example, since that was what you are talking about in your OP, I agree with you, if your budget is tight, and/or you don't really care about fit and finish and 'high end feel and precision', dead spots, etc., etc., listening to clips of high end basses you would never buy would probably be kind of a waste of time.
Since virtually no one can try before buying (these upper end basses have very low, or no distribution), clips might be the only cue the buyer will have regarding a high end instrument. I have only played one bass prior to purchase in the last 10 years. It's just impossible for most to do, unless you live close to Bass Northwest, or something.
Now, of course, if the clips suck, or if you are listening to them through some crappy little speaker(s), then they go from being 'possibly useful' to 'totally useless'.
That all being said, I've never bought a bass based on sound clips. However, I've eliminated quite a few from consideration and saved myself some grief and money based on hearing stuff I really didn't like on clips from a known, respected source.