You can also barter items for food, but this usually gives you less food than what you would if you managed to sell the item and buy the food.

Also, there is much of hidden food items in the game that do not cost money. I think there was at least one animal that dropped good food when you killed it. Some kind of deer or such in open plains, a bit east of Tir-Talath. For food, I can recommend the steaks in the Inn of Eternal Star.