Of course knowing the market price is good to be able to set the price. But you also have to figure out if your a Wholesaler or a Retailer. Wholesalers put them in the stores at a cheap price knowing full well someone else is going to buy it to flip it for a higher price. But, you get your gold faster, sometimes in minutes. Then of course you can price it at retail and wait a few days or a week depending on the item.
As for foods, use the addons listed above to determine the ingredient prices, and then figure out your real unit cost for each item you make. Remember, each ingredient makes 4 items, so keep that in mind. Most people will not pay more than ingredient replacement cost for foods and drinks, so the profit comes from farming or doing daily provisioning writs to keep your larder stocked. Purples might command a higher price, but I won't use my Frost Mirriams for anyone else but my characters.