Price aging marks down perishable stock as it ages. Instead of selling every lot at the same price until it expires and is thrown away, the price steps down as the expiry date approaches, so the product sells while it still has value.
The risk is selling below cost without meaning to. A floor at cost, with an explicit choice to go below it, keeps markdowns from becoming losses by accident.
In APFoodz price aging rules mark lots down as they age.