I don't know why the articles are making this out to be so complicated.

1. Take the price of the phone you want. e.g. iPhone 6s 64GB: $749.00
2. Subtract the value of your trade in to get the amount you are going to pay. e.g. iPhone 5c: $749.00 - $200.00 = 549.00
3. Divide in 24 equal, interest free payments. e.g. $549.00 / 24 = $22.87 a month

You might be forced to pay the entire sales tax upon purchase.

I think the statement reads oddly out of context because the case is about an iOS7 phone, where it's not 'impossible' (only burdensome) yet warning them that it will be impossible in the future. They're afraid that un-encrypting it now, just because it's not 'impossible' will mean that in the future they might be forced (by law) to make it possible, so they're arguing that they shouldn't have to do it, even now that it's only 'burdensome'.

Just providing my own anecdote to the conversation. Seems like the entire* country of Dominican Republic is using WhatsApp. From what I recall, BlackBerry Messenger had become the IM app of choice. People saw it as "free SMS". Everyone wanted a BlackBerry, just for the messenger app. Long after RIM had lost most of it's marketshare here in the US, it was still going strong there. Eventually though, they couldn't ignore the iPhone anymore, and WhatsApp was one of the few IM apps that worked across the phones. Now, black berry is dead, and iPhones have iMessage, but WhatApp has momentum, and much better group messaging features. I personally don't know of anyone in the US that uses WhatsApp without there having been a need to communicate which someone internationally that has it. Stop looking for users in the US. That's not where the WhatApps users are.

You can stream from your computer.

I don't see how you can price a comparable plan on AT&T for $130.
I have 4 phones on my family plan and everyone in my family would sure like an iPhone, but the value is just not there when you compare AT&T prices to Sprint.
You would have to find an AT&T plan that charges $40 for 2 lines since you need to add at least $90 in add-ons ($60 (2x$30) for iPhone data plan + $30 for family messaging) to match the Sprint plan.
The "Sprint Everything Data Family - with Any Mobile, AnytimeSM" get you, for $129/month:
    1500 anytime minutes
      free nights and weekends (7PM-7AM)
    'unlimited' pda internet
    Free anytime Mobile to ANY Mobile (this is huge!)
The closest similar AT&T plan would be the "Nation 1400 FamilyTalk w/Rollover® Minutes" plan, for a total $179/month and:
    nights and weekends are 9PM to 6AM
    free mobile to mobile only to other AT&T phones "from within your calling area".

Take a look at the Rich Ajax Platform Project.

Google Apps work without a broadband connection too.