While a tax is levied on iPods there is NO TAX on computers and computer equipment.

Apple Malaysia however have been quite competitive with Mac pricing. It's a little higher than Singapore/US but not by much. Some states in the US charge tax which makes buying in the USA sometimes MORE expensive than Malaysia, so what you see online may not be really what you'd pay.

Obviously the price can't be EXACTLY the same worldwide...

Some places are cheaper, some more expensive, some have better deals, some none at all. Buy where you can get the cheapest of course. Your warranty is international after all. However, be careful about buying at non-english speaking locations. The keyboard may be substantially different. Otherwise: go ahead and hand over your plastic.