Apple keeps a pretty tight lid on MFI though, right? As long as the box has MFI on it, it's probably legit, unless you're really looking on the grey market, I think.
I really doubt Apple is able to police the supply chain that leads to the check out counter of a convenience or even grocery store. There's no way to know that the MFI logo on the box is legit or not.
I don’t know how successful they are, but the whole point of MFI is to give Apple the ability to send the USG after you if you use the logo without permission. I mean, there are also fake Rolexes and fake Gucci bags, but those are the exception because the companies mostly do a good job of suing the violators.