If you list your boat and general location with your avatar, it will make the Forum's answers to your questions more pertinent.
Cruising cats vary a lot in size, for instance, and if you live somewhere you are likely to experience high winds that develop suddenly, that, too, would have to be factored into the answer.
Usually, dacron (polyester) is the material. The complexity of the sails is what adds most to their cost.
Getting personal here, our preferred method of buying
sails is to have two or more local sailmakers give us written estimates, then we choose the one who works best with us, cost is not the only input we consider. You want someone who will come measure the boat (to be sure everything will fit properly). And, IMO, you want to be able to get it made right if there is an *oops!* without having to ship it halfway round the world
to do it.