I'd say the same as someone who lives in Hong Kong and travels to Shenzhen with some frequency.

With one caveat, those folks selling parts definitely treats me with a lot less friendliness than they do with foreign buyers, especially when you're buying just one.

There are also varying level of quality when buying parts, especially batteries and screens. It's hard for repair shops in the area to charge higher prices for better parts, so there's definitely a huge market for screens that's slightly mis-calibrated, has a non-noticeable dead pixel and such. Customers in the area generally care less about those kind of quality.