> Costco electronics are often times priced very similarly to Best Buy [...] If Costco is breaking even on them, are you implying that also the other retailers are?
They break even in aggregate across everything that isn't memberships, but there is a bit of variability in margin, so, maybe, maybe not.
OTOH, brick and mortar electronics retailers have for quite a while had narrow margins and pushed things like high margin extended warranties to make profit (or, for the vast majority of them, just gone out of business.) Costco includes an extended warranty with purchase.
> Tons of people buy their Apple electronics at Costco, so I have to assume it is a significant percentage of their revenue.
Probably not. Apple electronics are big ticket items, but people aren't buying new iPhones or MacBooks all that frequently. The revenue from a person buying a MacBook and iPhone every other year is dwarfed by that of a person buying groceries every week.