http://www.growweedeasy.com/marijuana-symptoms
a myriad of symptoms that would mess up your 50-100,000 plant super crops, thus resulting in 0 profits and bankruptcy of anyone who thinks a person or corporation can easily farm and just spray chemicals to fix things. Anyone who grew would know you can't spray chemicals during flower on your buds as it comes out in the smoke and is potentially harmful to the consumer. Not to mention mold that can cause even more issues and ruin your harvest.
Certain strains require optimal conditions to grow, frost and cold would slow your growth to nothing, heat and humidity would kill off your plants, a more compact grouping of plants increases the chance of mold and pest infestation, thus limiting locations within many countries. Lack of fertile farmland and the fact that cannabis as a weed leaches nutrients from the soil on a massive scale, making your farming areas need to have crop rotations three to four times higher than many others. Planting crops on a massive scale would result in chemical and nutrient run off into water sources or leeching into the soil thus causing serious environmental concerns.
Importation of crops from other countries (due to the above factors) such as a southern to northern hemisphere or the other way around in many locations would increase distribution costs if your non-hydroponic global enterprise existed (or are you one of those people who think America is the only country that matters, when India and china have a population of over 1.3 billion people each respectively and would make a much higher consumer based market share).
The simple fact is you have not really thought about global economics or current agricultural practices, farming land worldwide is a scare commodity that needs to be preserved as the degradation and sustainability of pastoral land would become more unusable thus resulting in lower food production and higher food costs. Do you really think many countries would consider allowing a recreational substance to take priority over food production. Look at china for example or India that have massive populations and produce a huge range of consumer goods, their farm land is scarce and mostly used for food production, would corporations be able to use that land for production of super crops of cannabis as you state, and what ripple effects would that have to consumers for other products.
If you have had farming experience your view seems kind of short sighted and limited to the resulting prices of cannabis only without considering the costs of production, the difficulty of production of a plant that suffers from a range of ailments (many capable of infecting entire crops), and the sustainability of environmental resources.
Any or all of these factors would never result in cannabis costing $10 an ounce, unless wait it's legal for everyone to grow, and where are the corporations then. it would result in seed companies having the major stake hold in cannabis production, massive production for seed purposes only, and where do most of the strains that are formulated come from today?
Hydroponic or indoor grow operations.