The only reason food hasn't become too expensive is wealthy people don't have a reason to go out and buy up all the food. They do, on the other hand, have reason to go out and invest.
This is, however, starting to fall apart for goods that don't normally have reason to be bought up. In other words, folks with capital now realize they can hoard those resources as well in order to price gouge. This is most evident in consumer electronics as of late.
Usually, these aren't super wealthy individuals, but instead folks who have been priced out of traditional wealth building like stocks / housing. They may not be able to afford a down payment on a house, but they can sure as heck spend a few thousand buying up consumer goods hoping to gouge others.