Well, I am no expert on these issues, but here's what little I know of.
In many cases, manufacturers pay regional distributors a set of amount of money for expected warranty repairs. So you have a distributor for U.S., a distributor for Canada, a distributor for Singapore, etc.
Not all regional distributors pay the same price for the same product from the same manufacturer. The U.S. distributor probably more than the Singapore distributor for the product from the same manufacturer.
Sometimes retailers can purchase products from overseas distributors at lower prices, bypassing their regional distributors. Those products are then called grey market goods. Because the warranty repair is provided by the regional distributor, they made no profit in the retailer selling a grey market product, and undoubtedly the regional distributor will be unwilling to provide warranty repair.
That's why manufacturers/regional distributors designate "authorized dealers," because these dealers agree to exclusively purchase products from the regional distributor, and will sell these products at a price level that the regional distributor will make a healthy profit on. And in turn those products will be covered under this particular region's warranty.
Also, if a big authorized retailer cannot sell all their inventory, they will sometimes sell them to other unathorized retailers at lower prices. This is not strictly legl. And in the process, these products are turned into grey market products as well. So in turn, these products wont have warranty.
So sometimes when you find dramatic differences in price on the same product from two different retailers, always check to make sure it is not a grey market product. Otherwise if you purchase a grey market product or from an unauthorized retailer, you may lose your warranty.