I can't help but jump into the HK debate. On the majority side. I have to wonder if he's buying 2nds/knockoffs - or has a Nike connection. There's no reason there would be deals in HK: a) tons of rich people; b) (unfortunately) not many tennis fans - too many clowns with Man U scarves around their necks in hot weather.
I do occasionally find good deals at GigaSports and Royal Sporting House (back when they carried tennis stuff) - but most things are higher than US list prices. And some RF stuff doesn't make it there - or they just one of every size. And as @syke points out, you have to be careful - try everything on - sizes are often different.
Spotted a shop in Tin Hau last trip but didn't have time to go in.
@syke: yes, courts (and pros to hit with) aren't cheap - land is scarce.
"I jump in it!" Russian Billionaire, DirecTV Commercial...