I'll echo the reply about cost-per-mile vs cost-per-week. Sails won't wear if stowed properly and kept covered to prevent UV damage.
I did a quick calculation and came up with a cost-per-mile for sails of 28 cents. ($6k for main and jib, lasting for 7 years at 3,000 miles a year). I sail an Island Packet 38.
Hope this helps,