Good price?

I'm currently in Hong Kong and am considering buying an EF-S 17-55mm from Wing Shing - the best price they can offer is 7,900 HKD (641 GBP / 1,019 USD).  Amazon sells it for £740, but since there would also be transaction costs (debit card payment) and a lack of guarantee once outside the country do you think it's worth it?  My camera is an EOS 550D.