Well, real estate markets in PRC and HK are another issue; but just for going to have dim sum or buying fresh fish and vegetables to eat, there used to be a big savings, and these HKers felt they could really enjoy the value in China when they stay there on the weekends or holidays. But simply not the case anymore, so why bother going up and fight the crowds at the border?

And you worry about food safety. At least the HK government does occasional spot-checks on the imports. Up north, there's no such thing. Tourists don't really have to worry about it, but if one goes there every other weekend and spend 40-50 days in China a year, it becomes an issue.