Apple now provides local currency billing for the App Store for 24 countries and territories around the world. That means that an app priced at 0.99 USD in the United States is priced at varying amounts around the world, for example 0.69 GBP in the UK and 6 CNY in China.
Of course, due to changing currency exchange rates, that means that users some countries end up paying more than others. We crunched the numbers for a "Tier 1" (0.99 USD) app using exchange rates from xe.net for 14 November 2012, to get this ranking:
As you can see, Norway and Denmark are currently the most expensive, costing 20% more than an equivalent app in the US, while South Africa has the cheapest apps, costing 10% less than the US.
Of course, a raw conversion to USD doesn't tell the whole story. People in different countries have different spending powers.
The Economist creates a famous "Big Mac Index" which compares Purchasing Power Parity using the price of an item available globally: the Big Mac. We used the numbers for July 2012 to compare the price of apps and Big Macs.
By this measure, India, Hong Kong and Russia have the most expensive apps in the world, with burgers around 2 times the cost of an app. By contrast, the lucky Swedes can purchase 6.9 apps for the price of a Big Mac (7 SEK versus 48.4 SEK). The US also has relatively cheap apps (or expensive burgers), clocking in at 4.4 apps per burger.