Most Americans buy groceries from a large corporate-owned store that they drive to and has everything, which compete with other large corporate-owned one-stop-shop that you have to drive to.
The older I become the more I realize how absolutely devastating the development policies of sprawl and low-density have been to all areas of human endeavor. You can't have effective competition without density and an ability to start extremely small.
This is a good metaphor for Net Neutrality. Maybe most of the US doesn't understand Net Neutrality, because they are trapped in their strip-mall big-box store hell, and don't know about real free markets IRL.
The Saturday morning farmer's market seems a reasonable approximation of these Chinatown markets at a sustainable scale for smaller/less dense regions. But really, population density is the magic sauce for demand in cases like this.
But a lot of places like this were eventually abandoned or demolished, except where they could be maintained or redeveloped as a tourist attraction, like Cincinnati did a few years ago. http://www.findlaymarket.org/
Actually, compared to farmer's markets, the big difference is the network of small-scale independent warehouses. This isn't farm-to-consumer or farm-to-retailer, it's just nimbler distribution.
I think price is good but the quality varies, as everything is coming up from NYC. Typically I buy scallions, onions and peas every month or so if I stop in to pick up a few other things like dumplings or sauces.
Probably volume. Chinatown is extremely dense and has such high foot traffic that it makes sense to operate without refrigeration, with goods stocked from neighborhood warehouses.
Most parts of the country don't have anywhere near that level of density, so the economies of scale wont work out like they do in Chinatown.