For several years, Apple has been offering users the opportunity to recycle the old products that take up unnecessary space around the house and offer them in exchange gift cards for the Apple Store. This year Apple of course also accepts iPhone 4 terminals for which offers up to $200 depending on the condition of the device. The idea is good and maybe it doesn't seem like a high price to you, but in the USA $200 is the price of an iPhone 4S for extending a subscription, so practically an American can buy a brand new iPhone 4S by giving his old iPhone 4 through the recycling program.
This program is run by Apple in any country that has an Apple Store, so theoretically you could get an iPhone 4S without spending a penny if you extend your subscription. Of course, in Europe, gift cards have a lower value, but also iPhone 4 subscriptions greatly reduce the price of the device, so you can certainly find the opportunity to considerably reduce the price of the device. Of course, this offer comes as an alternative to the direct sale of the terminal, so you ship the whole process, get the money quickly and buy the newest iPhone.
