For $100 over the 5C, the 5S offered A LOT of benefit.
Yep EXACTLY....
In Australia it is $529 for a 4S (yes 4S!!), $739 for a 5C and $869 for a 5S.
Other factor aside, here's my reasoning as a consumer:
1) 4S is oooold!! I can get one second hand for ~$200 or less, why would I buy one 'new?' They don't compare with new $500 Androids in terms of features/performance and really aren't a good buy. I bought one new when they were brand new and still use it (love it.) BUT I think Apple looks bad selling 3-year-old phones for $500. I'd cut them from the market, mainly because people will buy them and say 'man the iPhone is nowhere near as good as Androids... I got this brand new 4S and it's much slower...etc'
2) The 5S is THE phone to get. It's the newest, the fastest and has the most features. It costs close to a grand so is a considerable amount of money for most. Without quoting my income, I can afford that kind of money but would rather not spend it on a phone every year (hence why I use the 4S still.) I guess when push comes to shove I prefer having a new/reliable car (without a loan), annual trips to Asia/Europe/The USA with my partner, platinum memberships for my favourite footy club and my law school fees as I recently went back to school part-time. I enjoy having all of these rather than the latest iPhone every year. FWIW I pay ~$25 a month for my phone bill as I'm not on a plan and scoot around choosing the best deal each month (doesn't usually change too often.)
When I eventually upgrade (maybe when my 4S turns 4 or 5?) I'll probably get the equivalent of the 5S. To me this is the only option unless the 5C becomes a $300-$500 phone, in which case I'd consider buying last year's phone at a 50% discount every year.
3) The 5C... let's get real, it's just a 5 in a new case that apparently has a slightly larger battery. I actually like them but feel most people wanted to pay ~$500 for them, NOT $100 less than a 5S. If you're spending close to a grand and can get an infinitely better product for $100 more then why not?
IMO It's MUCH cooler than simply keeping the iPhone 5 on the market, but to be frank, why shouldn't I just buy a 2nd hand iPhone 5 instead? A mate offered me one for $500 when he got his 5S (the guy isn't rich but he's one of those... dudes who buys a new Mac Pro and iPhone every year because he can't live without having the latest and greatest Apple gear.) His money, not mine...
Anyway that would be my call. If times were tough, my 4S broke/became unusably slow and the $100 extra for a 5S was going to break the bank then I would buy a 2nd hand iPhone 5 instead of a 5C.
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Note: Think what you like... Apple has me feeding from their hands. I like Apple's ecosystem and don't want to buy Windows/Android devices. A few years back I was broke (went through a horrible international divorce and was unable to work full-time for as I was going in between countries for court visits...etc and had a bit of a breakdown.) She took my Mac (grab and run when clearing out her gear) and I was forced to go shopping for low-end gear.
Rather than buy a cheap PC I found a 10 year old Mac for ~$100. I'm the same with iPhones and believe that a significant proportion of Mac users are like this. We love Apple and will only buy Apple gear BUT we need the right deal...