Demand. Chinatown can do it because it's ethnic residents don't just want a great selection of produce, they demand it. They want it bad enough to fuel an entir

Demand. Chinatown can do it because it's ethnic residents don't just want a great selection of produce, they demand it. They want it bad enough to fuel an entire alternative supply chain. If the people buying Chinatown's produce were replaced by less-discerning customers, the produce markets would disappear overnight and the farmers would have to unload their current crops at cut-rate prices. Normal customers don't want it that badly. So supermarkets can't rely on being able to continually turn a profit on such a risky endeavor. A service doesn't just have to be ten times better than the alternatives to drive mainstream adoption. It also has to be something people want bad enough to pay to create an entire industry around delivering it.