There's also different Y580 models. Newegg's may be a slightly different model. I've found that unless there's a sale in the US, prices in HK will be comparable unless you're buying a parallel import US model in which case you pay more AND don't have a valid warranty.
Price.com.hk is basically a listing of products online. Shops will post their prices and info, and if you like the info, you can go to the shop and buy. Some of them offer online purchase/delivery options.
Also, I have a Y560p that I'm preparing to sell (just got a desktop) if you're interested. Radeon 6570m, i7 2630QM, bluray, 8gb ram, 640HDD, perfect condition since I have it hooked into a keyboard, mouse, monitor and basically leave it at home as a desktop.