The Economist publishes an index periodically that tries in a lighthearted way to shine a light on those economies where currency valuations are out of sync. They use the MacDonald's Big Mac (never tried one myself) as the benchmark. The reason for this is that there is a MacDonald's restaurant in every meaningful country in the world.
The current index might show a couple of things:
1. Being close to cheap raw materials doesn't secure low prices - (Brazil, Argentina, Uruguay)
2. If you want to start a burger restaurant you should avoid mature markets where competition is greatest - strong currency but low prices (UK, and Japan)
3. If you have an alternative (Kebab stall maybe) set up where the market is unconvinced by the Big Mac product - the cheapest deal (India, Mexico, Malaysia and Hong Kong)
If the world's economy gets much worse we may dependent on bartering Big Macs - if so you should pick Wengen for your next skiing holiday rather than Aviemore, probably not a difficult call!
Datagraphic completed the same sort of exercise with Starbucks (or as I call them OURBUCKS following the UK tax spat last year). They seem to be creaming it in Japan and China and again the UK is pretty much on par with US.
Nice graphic from Datagraphic?!