I think a few here are often charged more too if they are not locals.

Most merchants will give up on the Guilo price right away if you call them out on it.  They still want the sale with their regular profit.  If the price seems just a little higher I usually don't complain (on the mainland, not HK) because I know I make more money.  It doesn't hurt me.  i would never do 1.5x or 2x what I thought was the regular price.

I don't think I've ever tried to return anything in HK, and in China you almost never get a receipt anyway.

As for WG, some do it for profit, some do it because they are scared.  They usually do not back down from the price.

I'm pleased to say the Hong Kong Consumer Council is dead wrong: you CAN get some satisfaction if you complain ...

I once met with a Philippina I'd met online, and she came to Hong Kong with her friends - so she's both completely green, and also carrying a wad of cash to buy a digital camera.  Goes into the first shop she sees in TST, and gets ripped off big time (something like 3x the street price of the camera she bought).  

Now... I know all sales are final, and I know the price is whatever is agreed between a willing buyer and a willing seller ... so the bad news is that anything is possible in Hong Kong ... but, what the hell, the good thing in Hong Kong is that anything is possible.  

So I go with them (white knight suit on) and politely describe the situation to the sales guy.  Politely that is, but loudly ...
... pretty soon I'm describing the situation to the shop manager ... still very politely, and still very audibly ...

Obviously he wants us out of there as quick as possible, so he can sell to other tourists

Cut a long story short, he offered a solution which I looked and my friends and they agreed it was OK by them ...

Oh, on another situation I managed to get myself caught out overpaying on a new tablet for my work by not paying attention to the small print in the specification.  Again, we negotiated a solution that cost me some money but nowhere near as much as keeping the tablet I didn't want would have cost.  

So yes, you can complain if you find out after the fact you've been ripped off.  

But so much better to spend a little time shopping around first.  You can find GREAT deals doing that.

Best to stick to the bigger chain shops like Fortress for electronics. Their prices are
Usually pretty good.