Why is the iPhones 5s cheaper in the US?

I want the iPhone 5s but I saw some videos and its £549 for 16GB and in the US is only $199. Why do they get to play less?

It is not cheaper it comes in a contract where you have to pay a certain amount of bill monthly.overall cost will be high

For one it's an American product and two currency differences are a factor. The pound is worth more than the dollar. So you pay higher prices in your country than you would in the US.

In us you can take iphone on contract to a carrier and you can pay monthly some amount and it will be locked to that carrier
if you want unlocked then uu have to pay full pay which of around $550

Because apple is based in the US, The US is the biggest buyer of apple products, and it had all the iphones first, The iphone will cost the same in UK though. $199 on contract (£129) and $649 off (£421)

549 pounds is for the unlocked version while 199$ is with 2 year contract!

Because United States is the Home Country of Apple Inc.therefore they are surely going to give extra benefits to their country men. These are some of the reasons for that:
1.US is their Home Country.
2. They don't need to include shipment costs in prices.
3. They don't need to pay any extra taxes or clearing costs.
4. They need to retain their spot in their home country, and need to increase their sales as they are loosing ground in US. (Currently iPhone 5 is at number 3 while top 2 spots are captured by Samsung Galaxy Smartphones.)
5. Europe is the Richest Continent, therefore they are covering all of their costs and profit difference from this region.

I see pretty good reasons for the price difference.