I hate to be a nay-sayer, but I have come to the position that there is no such thing as a good deal on a sail. You CAN overpay, but in general, you get exactly what you pay for. Used sails are always priced as pretty much an exact percentage of their remaining useful life. And, new sails are pretty much priced according to materials and features. Well-made sails tend to be priced accordingly, and sails with manufacturing shortcuts also seem to be priced accordingly.
I am all set up to make my own sails, and can muddle my way through that process, and even that doesn't save me any money - in particular when I estimate that a sail that I make will last about a season or two less than a sail made by someone who knows what they are doing. And, certainly not if my time is worth anything.