After a few weeks, I think I honestly have come to a pretty solid reasoning behind the 5c.
Years ago Apple used to offer a Macbook and a Macbook Pro in their line up. The Macbook WAS cheaper, but it was not marketed as the "cheaper" product, it was marketed as the more "fun" product, the product for younger people, the non-professional offering for people who wanted a Macbook, but didn't want to pay the premium for the metal casing or the higher specs that they didn't feel they needed. You were given a very nicely equipped machine, about 3/4's the performance of the Pro line and a choice of colors (white polycarbonate and black polycarbonate).
Then...they realized that the market wanted lighter, slimmer and sleeker...so the Air took the place of the "entry" model. Again, not marketed as a "cheaper" Macbook, but marketed towards people who did not need the powerhouse Pro offerings, and were content with the slightly lower specs at a slight lower price. The Air became the new standard entry level offering, but it was never even thought of in the "cheap" frame of mind, and that is because the media never thought of it in terms of getting the product into an "emerging market", this was a product for the normal consumers that Apple already had targets on.
The 5c, I feel, is IDENTICAL in this situation...the major difference being the fact that the iPhone 5 and now, the 5S, were already so light, slim and streamlined that they really couldn't take the same approach they did with the Macbook Air, so what could they try? A reversion back to the "fun". Offer a polycarbonate iPhone that is a little cheaper, a little less powerful (for those who weren't concerned with the guts of the phone, which most consumers would never understand anyways), offer it in a slew of colors to bring some life to it...and market this phone for people to feel "unique" and "alive".
The media started this idea that the 5c was an emerging market savior. It was never intended to be a "cheap" iPhone, and there is an ENORMOUS difference between "cheap" and "cheaper", and this device certainly IS a "cheaper" iPhone, but it's not cheap.
Now some people will argue "What's the point of this device if it still cost so much?" And the answer is really pretty simple. They knew there was a market for people who loved the iPhone but were growing tired of the same cosmetic form...this forum alone reflected several opinions that the simple "Black and White" color choice was growing stagnant, and that was probably echoed around the market pretty heavily as well. At the same time, Motorola offered a new customizable color pallet for people to get the feeling they were getting a "unique item", something they created...so Apple's approach was similar, offer the colors Apple is famous for, and then offer a case program that can essentially change the whole color scheme of the phone, but remain true to Apple's quality and design standards.
Honestly, looking at all the people who have 5c's in my circles, and the really swell marketing campaigns they've come up with to really amplify their "unique" and "fun" approach, I'd say Apple has a pretty great thing in the 5c. I mean think about it, you're young, you want a new smart phone, but you're not one of us forum geeks that sit around looking at minute spec increases from every company, every year...the camera on the phone was already fantastic, so a few extra features may not matter to a person trying to keep their budget down but still own a top tier device...why WOULDN'T the 5c be very attractive to that audience?
And let's face it, while the 5 and 5S are sexy and sleek, they don't really "stand out" visually...they are more of a really "nice" design, but not a really loud design, and loud gets people into stores, loud gets people talking. I mean the negative publicity about the completely asinine idea that the 5c was an emerging market phone has put the 5c in the mouths of people who probably wouldn't have even cared about it (I'm one of them...I've grown more appreciation for the device just by trying to figure out what the point was).
That's just my take on it.
TL;DR - The 5c is to the 5S what the regular Macbook/Air is to the Macbook Pro.