If you purchase food items, and then wait for the next day to start and re-enter a settlement and go to the market, you’ll see that the displayed price for which the items were “bought for” is reduced (compared to the real price you paid) by a number matching the number of days for which the particular food items last.
This sort of makes sense, since it makes the “bought for” price relative to the remaining life of the food items, but it’s still misleading, since you’re expecting to see the absolute price so that you know if you can make a profit by selling surplus food.