This happens in the real world too. Imagine travelling to a poor country as someone easily identified as wealthy, for instance. It happens on a microscale within a given country too, if anyone identifies your wealth, you'll find prices creep upwards, especially for work of a contracting variety.
To really confirm this, try bringing two watches to a watchmaker at different times, one a $5,000 watch and one a $500 watch. Ask what a service costs. The gap tends to exist even if the movements are the same!
Interestingly, here in China I am currently editing and shooting a documentary on a foreign community and just yesterday hit on an interviewee's comment specifically to the effect that this does not occur, ie. locals treat everyone equally. The way this was explained was that, if you ask the price for something in a market, wait 10 seconds and eavesdrop on a local requesting the price for the same, it never differs. This is also my experience (after 15 years). I wonder if perhaps this area (China's most ethnically and linguistically diverse) simply has a fair treatment norm based in pluralistic history.
That is the exact opposite of my experience of Chinese markets (Beijing/Xian). Asking in English is quoted at a markedly higher price than asking in Chinese. Not to mention that it is haggling-based, and final price was even more dramatic when using Chinese vs English.
Even if it's a Chinese person asking in Chinese, the results can differ dramatically merely if they're seen to be accompanied by a non-Chinese person. If you want the best deal, not only have a native ask for you, but hide before they do!
Sounds like Yunnan > Beijing. The comments were about food markets and normal things, not for luxuries or tourism-style purchases. Also, after you have been here awhile you can tell the accent - a Beijinger asking with a local accent probably gets significantly different treatment. Luckily people here don't seem to engage in such games, though always appreciate those who put the effort in to reproducing the local accent.
To really confirm this, try bringing two watches to a watchmaker at different times, one a $5,000 watch and one a $500 watch. Ask what a service costs. The gap tends to exist even if the movements are the same!