The sails will cost around $3k to replace with BASIC sails.
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I would be VERY leery of purchasing this boat as much as I like CS30's. I think you are gonna find a lot of expensive surprises. If you got a GREAT deal and know exactly what you're getting into and can deal with the expense fine...but 7 years on the hard take a big toll and I think you are gonna have core deck and deckhouse issues as well as engine issues. These are difficult issues...not just finding a leak and stopping it!
I may be wrong but that is my impression given what you have said.