media prices

I don't understand pricing for media here. I don't think it's an issue with Singapore but rather just international media. Magazines are super expensive here... so I never buy them. For example- Something like Time magazine or the Economist should cost what, like $3.95USD newsstand price? That should be about $5.80SGD according to XE.com Conversion (Oct 15, 2007). Instead those magazines are more like $12SGD here. Twice the price! So I guess it's the shipping charges etc... If that were what the extra cost was for I could even understand but I don't think that's it. For example: The 3 books I purchased today (from the post below). I'm using XE.com Conversion for all these calculations on October 15th 2007- $1USD = $1.465SGD

Asiaddict:
Listed price on the book: $15USD. Price in SGD on the tag: $26.28. Effective exchange rate: $1.75SGD = $1USD. With correct exchange rate: $21.99SGD

Pyongyang:
Listed price on the book: $14.95USD. Price in SGD on the tag: $30.25SGD. Effective exchange rate: $2.02SGD = $1USD. Wah, not so good this one! With correct exchange rate: $21.9SGD

The Shock Doctrine:
more complicated
Listed price on the book: $12.99U.K. Price in SGD on the tag: $26.70SGD.
well $12.99U.K. is $26.5USD so that should mean $38.8SGD... but the price tag only says 26.70SGD! which is only $18.2USD.... and there was a discount of 20% off the listed SGD price. Effective exchange rate: $1.01SGD = $1USD. With correct exchange rate: $38.8SGD

So why so much variation? is it just the day they happen to convert the price from USD to SGD and print up the price tag? I doubt it (though this does happen... cannot reprint price tag in SGD each day to compensate for currency fluctuation) since currency doesn't fluctuate this much! Is it related to the publisher? or location of publication? Or content of the work? The first two books were published in Canada and the third was in England. I do understand it takes money to ship things overseas but I don't understand the differences in prices since there doesn't seem to be a methodology to it based on location. Yes, Singapore used to be a colony of the British but wasn't Canada also? Oh, never mind, maybe that was the French. I think the U.S. was...^_ ^... but I don't have any reference points for prices from U.S. published books. Oh, also foreign newspapers are also very expensive.