We seem to be missing a trick here.

A Rolls Royce, if you test it as such, can get from your house to the supermarket and back. So can a 20 year old Lada. Both can carry the shopping, both can get your responsible adult in the passenger side. Both have four wheels, a paint job etc etc.

Likewise, my lads when they were children brought home paintings they had done at school, and we put them up pride of place in the kitchen. We also went to The Louvre to look at the paintings there when we were in Paris.

A stradivarius is of course a well made instrument, to decent tolerances, fine workmanship, well set purfling, decent finish. Of course it sounded ok. Over time, it sounded even better. of course, Nobody has living memory of it's performance in the first ten years, when the sound will have been changing.

So, what makes it a good violin? Especially if the judgement of the listeners, as subjective as it is, is taken at face value?

You have to think of the time it was made. The years 1500 to 1700 are the years the trees were growing as most 'Strads were made in circa 1690 - 1720. The spruce he used for the tops where the sound resonates and develops enjoyed fairly consistent weather over time and the rings were uniformally spaced and densely packed due to the mini ice age, to a far greater extent than spruce used since from most of the world. (I used this argument as part of my PhD in vibration, so have been known to rattle on about it from time to time. That's another reason I like my carbon fibre Rainsong guitar, consistency, other than the prat trying to play it.)

The upshot was consistency, and that gave him a good reputation, especially for newer instruments still to get to their best. The reputation grew, and then many of his instruments developed other provenance such as one owned by Napoleon, Byron etc, and the violins you can see and know that many of the great composers have heard that actual instrument play their music.

Judging art by utility isn't the most useful exercise? Oh, and lets be fair. My £200 instrument is a fiddle. Stradivarius made violins....