iPhone-like items are a very small part of anyone's annual budget. What matters are housing costs, transport costs, healthcare costs and quality of life. All of which are highly variable depending on location.
The iPhone itself may be a small part (depending on your budget) but wireless plan costs also vary widely. I know that UK/EU plans are substantially cheaper than the US where many pay $150+ per month for a couple lines.
Wireless prices in the USA are higher than any other country I've been to, developed or not. Nevermind the absurd contracts.
In Taiwan, for example, I got a 3G phone plan for $40 month-to-month, unlimited data, and consistently ~20mbps download speeds.
In developing countries like Thailand or Central America, I can get a 3G card for 60 days and 1-2GB for less than $10. Speeds obviously aren't as good as Taiwan, but the basic access to Internet is way cheaper.
I don't think electronic gadgets are a good item for this comparison.
You might want to take a look at the Big Mac Index, which tries to give some measurement of how much your money is worth in another currency or country.
I mean iphone costs about the same anywhere in the world ( okay it's sometimes more usually not less (Brazil?)) so there's that...