i'm probably not supposed to divulge the inside info on retail margins but here is a brief example.
the rods and reels folks buy ( at the busier shops ) such as the trophy xl, shimano convergence, berkley , shimano calcutta's, abu 6500's ect.. ect... pontoon boats, float tubes, waders, so basically the big ticket essentials, are in most shops priced as "loss leaders", meaning full mark up is not possible because the prices on these items get you thru the door and the retailer is making very little as far as profit.
the calculation used to come up with an end price is different for each shop because retailers get dealer discounts for volume purchase. This is why the walmarts and army and navy's can afford to have low pricing because they buy as a corporation and distribute to thier stores thus earning the maximum AAA dealer discount. Many shops can't earn theses discounts because they simply don't move enough of the particular product.
I'll tell you this, if a customer is walking into a shop and has the shop order an item that is not a standard stocked inventory item, the retailer is using a calculation based on the dealer cost x 1.45 to 1.73. with 1.73 being the standard. You go less than this on too many items and you will NOT be in retail for long.