Part of it is certainly the subsidization of conventional agriculture and the decreased cost of monocultural foods because of that. Part is the inability of the market to factor in true costs like pollution or decreased nutritional values. Part of it is the reluctance of the consumer to value clean organic crops over cheaper crappier foodstuffs. Small, niche growing is more labor intensive, and farm labor has been about mechanization for two hundred years, not better food or better environments...
Another part is the middle man, F-san is clear that excess cost is a function of too many hands in the food chain. Direct purchasing from local farmers keeps money in your town and region, gives the farmer fair pay for his services (he keeps more money), and gets you good food without the pollution of shipping.
Hai, Sensei!If natural food is to become widely popular, it must become available locally at a reasonable price.