My insurer has a standard €400 deductible on mainsails (some have €800).
The formula they used to determine the value of a used sail is %25 loss of value in the first year and %15 for every consecutive year.
(My mainsail got FUBAR'ed at Texel last year so thats how I know). <img src="http://www.catsailor.com/forums/images/graemlins/blush.gif" alt="" />