When is a hollowed-out, well-worn, foot-long hunk of wood worth 3.5 million dollars?

When it's a hunk of wood that was carved into a violin 267 years ago by the renowned violin maker Guarneri del Gesu.

3.5 million dollars was the extraordinary value settled upon by the tiny cadre of great violin collectors when violinist Robert McDuffie put together a consortium of investors to purchase one of del Gesus' almost mythically great instruments. The consortium has been assured that when the instrument is resold in 21 years, its value will be in the neighborhood of 24 million. Not a bad return on a 3.5 million investment.

Obviously the value of this, and other great violins, is not determined by any one factor. The value of the violin is not its age, not the quality of the tone it produces, n…