You guys are doing the common mistake here to look at the value of food from todays angle.
500 years back you could actually find food that was "worth its weight in gold", especially meat, salt and many kinds of fruits, and pretty much anything that rots easiely. All stuff that is pretty much worthless by todays standarts. Even plain grain could rise up to those values if the farmers had 2 or 3 bad years in a row.
Many german cities have the word "Hall" placed like a title in their names, which is the ancient german word for salt. That is just how valuable salt was back then, having it made you so rich that you named your city after it.
Spice trade, without the benefit of modern transportation networks (granted "spice trade" might be a bit of an ambitious description for what's going on, but valley herbs are relatively valuable as a foodstuff)?
This.