The main protections in the UK come from the obligation to show prices
Price Marking Order 2004
This requires traders to display the selling price of goods to consumers, except:
* goods which are supplied as part of a service;
* sales by auction or sales of art and antiques;
* products sold from bulk; or
* advertisements for goods.
The selling price should be:
* inclusive of VAT;
* unambiguous, easily identifiable and clearly legible;
* close to the goods or, in the case of distance contracts or advertisements, close to a visual or written description; and
* available to consumers without them having to ask for it.
In general, a trader must show the unit price of goods sold in bulk. This is where the goods are weighed and measured for the consumer, such as fruit and vegetables, and for pre-packed goods marked with a quantity or made up in a prescribed quantity.
Plus the obligation to not mislead on pricing (ie sell at the price indicated). I do not know if HK has price marking laws (very much doubt it) but without the requirement to indicate a price it is hard for consumers to protect themselves again people who just make the price up as they go along.....