I would think that specialised and expensive shoes have less markup than cheaper and more common shoes. But if the cheaper and more common shoes become 50% more expensive then there aren’t really any cheap shoes left to feed the bottom line…
The retailer & the wholesalers involved all have a reasonable idea about what people will pay for the products in question. The portion of that final consumer price that stays with the retailer is just the result of negotiation.
The retailer can likely buy decent alarm clocks from anyone, so alarm clock makers & wholesalers have no pricing power and the retailer can demand high margins.
But the retailer can only get Garmin from Garmin. If Garmin has done a good job promoting the brand, such that the retailer feels they have no choice but to stock it, they will have to suck it up and accept low margins.
People will go and shop around for the best price on a $300 item, but for a $10 item they'll buy whatever's infront of them, so long as it's not clearly outrageous.