I wrote this in another comment on branded devices:
Use a credit card instead but even better, do the simple math:
Carrier branded device: $99 down payment (depends on the credit rating).
Monthly bill: (Unlimited data) $70 per month
Taxes and fees: $10-20 per month
Monthly installment: $20 per month
Total monthly cost: $100-110 (depending on the regulatory taxes and fees)
Total cost for the device (provided that 24 months of installment is selected):
$99 + $100-110/month x 24 = $2499-2740 (depending on the taxes).
You can trim this by buying it outright and put T-Mobile prepaid on.
Then we have the method I always use:
Unlocked Xperia Z: $599
Monthly cost: $30-49 per month (T-Mobile prepaid $30 plan, Straight Talk (T-Mobile) or Solavei (T-Mobile)
Taxes and fees: $0
Monthly installment: $0
Total monthly cost: $30-49
Total cost during 24 months: $1319-1775
Savings: $965-1180
Don't tell me that a carrier branded device is "cheaper" than the unbranded, unlocked version and please don't complain about device costs when you are ready to sign away $2499-2740 when the alternative saves you approximately $1000.
I don't get people that complain about buying a device unlocked when they are ready sign away a huge amount of money. The same people seem to understand that computers don't cost $99 and then $100 in Internet Service or that TV sets are $199 paired with minimum cable package of $75. They can buy a computer for $699 or a TV set for $699 without complaining. But when it comes to a smartphone, it is a lot of moan and gritting teeth when the price tag says $599 so they prefer to pay $2499 for it instead since they are forced to sign a contract.
T-Mobile don't do contracts any more, I know that perfectly well but the fact remains: a T-Mobile branded device with 24 months of installments paired with service cost a lot more than the unlocked edition.
To me, $2499 and more is way too expensive for a smartphone so I always opt for the cheap route and buy it unlocked. I got a superior device, no carrier bloatware at all, no carrier branding at all, updates straight from the manufacturer, unlockable bootloader (for the Xperia Z) and everything the way Sony intended.
So buying a T-Mobile Xperia Z and truly believing that it is "cheaper" is a less optimum action. But it is obviously not my money, those that want to give $1000+ to a carrier are free to do so. We live in a free world.
But they should not even try to claim that those extra $1000 somehow is a "cheaper" deal. It is like claiming that $10 is more than $20 ($20 is 5 + 1 x 15 in this case).
I prefer to have $1000 in my wallet rather than giving them to a carrier and then "enjoying" branding, bloatware and locked bootloaders.
As I wrote, I wonder how people can buy a new computer, a car, a TV etc without subsidies but when it comes to a phone, then it is disaster to pay $599 and a cheap monthly plan when you can pay $1000 more just in order to think that "I paid only $99 for the device, it is cheaper than $599!"