You can't extrapolate total returns based solely on forum posts. Most MacRumors users are probably much pickier for one thing. For another, a lot of the replacements are refurbs -- consider where refurbs come from.
Does the how really matter? Apple's financials are out there and they're obviously making money despite your assumption that there are such massive returns that they can't be making money. Where do you think the mistake lies? Even without knowing, it's likely that the side that's relying on assumption and speculation rather than the side reporting on hard numbers is the one that is mistaken.
Let's also not forget the "hoard mentality" that Macrumors causes. One person finds a small amount of light bleed, slight yellow tint, or the tiniest scratch on the back of their new phone and suddenly "everyone" sees it on their devices. If you are like 99% of the population, you've never even been to Macrumors and thus don't even know about these "issues"....