There are many reasons for different prices for Apple products outside of the US.
- sales tax. This is around 20% in many countries and factored into the advertised prices, while the prices listed on apples US website are without tax.
- currency conversion. Apple operates mostly from the US, and has contracts with suppliers in US$. For sales in countries with a different currency, they a) have some extra cost to convert and transfer the money and b) have to protect themselves from fluctuations in the exchange rate, either by buying insurance or by adding a little premium to the local price
- small market effects: Localization of products (keyboard, language), also they have to hire a lawyer to make sure the product doesn't violate any local regulations.
- customs fees: These are mostly gone now, but maybe not everywhere
and finally:
It is customary to adjust the price of a product to how much customers in a given country are willing to pay. For example, German cars are more expensive in Germany than e.g. in Spain, Italy or the US. Germans are happy to pay more for what they think is a better product, while people in Spain just buy a French car if the German one is too expensive.
It's probably too easy to ship computers for this to have a big effect, but one shouldn't forget it.
Some companies are really ruthless. US branded jeans are a good example... the sales price in Europe is often three times the US price.