Stradivarius violins are invariably played and sometimes owned by soloists, who either literally play solo, lead a concerto, or occasionally play with a pianist

Stradivarius violins are invariably played and sometimes owned by soloists, who either literally play solo, lead a concerto, or occasionally play with a pianist or as part of a small ensemble. First violin in an orchestra will usually have a more modest instrument. Edit to add: of course there's a lot of Veblenisation in music, and this gets silly when people who are really collectors try to do music and end up being just a more extreme kind of consumer. Hifi, guitars, synthesizers, and recording equipment are full of this - plenty of moderately wealthy doctors, lawyers, financiers and such of low-to-average talent buying vintage or custom signature whatevers and displaying them proudly on social media. But there are also professionals who are super-sensitive to tone and expression and have a (literal) track record of making choices that audiences respond to. Some of them have impressive collections too, but they're able to justify them for specific creative ends. The difference is that if you take an expert and give them an average instrument they'll do miracles with it. If you take a collector and give them a room full of classics they'll produce mediocre mush. But give an expert the classics and they'll wring an extra level of musical credibility and interest out of them. That zone is out of reach of the collectors, but audiences still appreciate it and pay for it when they hear it.