Indeed, a better way to fight this would be to start making the cost visible to your manager. Just start a spreadsheet, "item cost" vs "total company cost", resulting in "Cost overhead". Just hand these to your boss each month. No snarky comments, no aggression, just "Look, I have gathered some interesting information".

Once he sees a rather ridiculous cost overhead right there on paper and ideally even verfiable with your orders through other systems, interesting things happen. More often than not, management didn't know the excess of the situation.