This is just reflective of inequality. I don't know about China specifically but in other asian countries that I know, most locals buy their ingredients at the

This is just reflective of inequality. I don't know about China specifically but in other asian countries that I know, most locals buy their ingredients at the market, and grocery stores target richer less price-conscious consumers. So it's certainly possible that the markup that the grocery store applies is greater than the cost of cooking and delivering the food, but that doesn't mean that it's cheaper than buying the ingredients at a market and cooking it yourself.