Stradivarius – how much did they cost back then?

Stradivarius violins today can sell in the millions of dollars, but how much did Antonio Stradivari (1644-1737) originally sell them for? It’s my understanding he only sold his violins to the nobility (Princes, Dukes, Bishops et al), probably the main reason that some 600+ instruments still survive today. However, it’s unclear to me just how much they actually cost. Were they astronomically expensive or just expensive? I’ve asked several professional violinists this question and nobody seems to know. So I’m turning the question over to the Web. Anybody know?

UPDATE 10/9/09
Looks like I *may* have found the answer in an old newspaper on the Library of Congress site — from The Amador Ledger, December 21, 1900

Costly Violins
The current value of Stradivarius violins in London is said to range from £80 to £800. In Stradivarius’ own time one Cervetto of London received a consignment of the master’s instruments which he was commissioned to sell for £4 apiece. But he was obliged to send them back, as no Englishman at that time would buy them at any such figure. Stradivarius himself is said to have asked a price of 4 louis d’or for each of his violins.

“Stradivarius himself is said to have asked a price of 4 louis d’or for each of his violins.”
4 louis d’or? According to Encylopedia Britannica, “They had a value of 20 francs.” So then, apparently the equivalent of 80 francs is what Stradavari sold his violins for – and a franc could buy what circa 1700? Anybody know?