Buying at a low price and selling for a higher price is a large part of Port Royale 3, this list gives rough prices at which to sell (higher price) and prices to buy at (the lower price).
Sell Buy Wood 57 40 Bricks 57 40 Wheat 57 40 Fruits 85 60 Corn 85 60 Sugar 85 60 Hemp 85 60 Textiles 250 200 Metal 130 99 Cotton 85 58 Metal Tools 350 255 Dyes 170 125 Coffee 250 180 Cacao 250 180 Tobacco 170 125 Meat 500 370 Clothing 800 555 Ropes 260 190 Rum 450 335 Bread 250 180