Yes, I've been listening to those sorts of explanations the whole of my business life.
I've also been on the opposite side of the table when very carefully costed/priced items have been presented to the MD for sign off, and he's red lined various things and inked in the price he "thinks" the market will sustain with absolutely no reference to actual cost, margins, overhead contribution, etc.
Like I said a basket of goods adds up to the similar total cost, which rather negates your arguments regarding various cost headings, but individual items are huge margins apart... someone has had the red ink pen out...have a look and it soon becomes obvious.