I would just like to add, there is definitely economical benefits in buying your own device, even in the US. T-Mobile offers a discount on contract plans, if you buy your own phone. While AT&T/Verizon/Sprint don't give a discount on their contract plans, all three have various prepaid options that are cheaper than contract pricing.

For example, T-Mobile has a $60 flat price for unlimited text/voice and 2 GB data, which is far cheaper than their contract price. Similarly AT&T Go-phone has cheaper prices.

Next, there are various MVNOs that resell service from the big 4, and they also have much cheaper price on prepaid. However, I have noticed that US consumer are almost universally unaware that such cheap plans exist. Part of it is that prepaid is seen as something used by people with low credit-worthiness, and other reason being that the subsidized contracts make it possible for far more people to have high end phone than normal. I have met quite a few people with iPhone, who would never be able to purchase it if they had to pay $700 upfront in store.