I buy from a wholesaler and the price changes every week. Will my food cost keep up?

Yes, as long as you receive deliveries through purchase orders. When a delivery arrives, open it on Menu → Purchase orders and type the cost per unit from the invoice beside each line before pressing Received. Each ingredient's cost per unit then moves towards what you just paid, in proportion to how much you bought, so a dear week pulls the average up and a cheap week pulls it back. Every recipe that uses that ingredient shows the new food cost the next time you open Recipes & food cost. Nobody retypes prices. If you buy without an order, the cost you typed when you first added the ingredient stays until you do. Recipe costing follows the market only if the invoices go in.