Stradivari violins

One of the most expensive musical instruments is Stradivari violin. According to a 2004 Forbes article, the luthier made around 1,100 violins and 650 are left. Right then, the world record is kept at $2.03m by a Strad violin called "Lady Tennant". But now, go to the website of Stradivari society, it's said the record is now set at $9.5m on a Strad violin named "Barrow" by a Russian collector. While this is astonishing, the cello "Dupont", also fabricated by Antonio Stradivari, previously owned by Rostropovich, has been acquired by Japan Music Foundation at $20m. I am curious what price "Davidoff" would be sold if it's on market one day, which is owned by Yo-yo Ma.