I honestly can't be mad at this point because what they SHOULD do is sell cables in bulk packaging to the Apple store, and then when they sell a phone they say "Do you need a USB cable? Free with the phone." If they say "No we're okay I've got hundreds of them by now" no problem, if they say "Yeah in fact can I get two?" Sure. Same with chargers. Of course this is Apple we're talking about, so they're probably $69.99 each.
I’ve had one apart and to be fair they are not carelessly made. They’re jacketed in soft silicone under the braid and have thicker than average stranded conductors. You can totally use whatever cables you want, but theirs are built a little better than you’d think and they just feel nice.
I could understand if you were buying a pay-as-you-go phone on the cheap... but this is an iPhone you're talking about. What's the minimum, $799? I think they can afford to toss a cable your way if you need one.