Production costs may well have risen, but so will cost of raw materials, cost to transport the raw materials, energy costs for manufacturer, costs for the transport to the warehouse, warehousing costs, transport costs from warehouse to DC, DC storage costs, transport from DC to stores, stores energy costs, increased interest costs for all of those providers etc etc etc.
I'm not saying every cent increase is justified, but with that many links in the chain from a potato in the ground to a packet of crisps in your hand, there is a lot more than just production costs which impact the cost of goods. And while the supermarkets don't seem to be doing it very tough, many of the other links will be on very tight margins, so can't absorb any further costs.
Production costs includes raw materials.