The pricing between HK and Beijing is much reduced these days, definitely a lot more than it was when the first Apple stores opened (you can compare prices between apple.com/cn and apple.com/hk if you don't believe me). The days of the yellow cows are mostly over, and have been on decline for a few years now (they no longer hang out at the Sanlitun Apple store as of 2016, for example).

I don't think ANY company can afford to leave China these days. Google only got away with it because they weren't making much on search in China.