Last year I did a price comparison of Apple products in different countries because I was going to be in those countries, and wanted to find out which was the best place to get stuff. For instance, for the 13' MacBook Air, the prices (this was early Dec 2010) came to:
Australia -- AUD$1949 = USD$2046
Singapore -- SGD$2388 = USD$1857
Hong Kong -- HKD$12488 = USD$1615
USA -- $1605
These prices are from the respective Apple online stores for each country, which includes free shipping and any sales taxes where applicable, and you can see it's not a trivial difference.
Generally, in Australia, there are many things if you bought them off-the-shelf in a traditional shop have a huge markup than if you bought them online from an overseas vendor, even with shipping costs added in. It has reached a point where local major retailers have been complaining and asking the government to scrap the $1000 GST threshold for imported goods, claiming they were being disadvantaged, and they even took out ads in the newspaper to that effect --
Abandoned retailers try Boxing Day ploy | News.com.au
That's one reason I bought my TwelveSouth Compass from a US vendor rather than the Australian Apple shop (or indeed any Australian seller), and paid a third less for it.
The fact of the matter is, if local retailers sell things with a huge markup, your Internet-saavy shopper will find elsewhere to buy more cheaply.