Great feedback as I build out my knowledge so that one day I can go for it.
I attended the Consumers Electronic Show in Las Vegas this year and sat next to a hydroponics expert from Canada who was formerly in a rooftop hydroponics start-up. He decided to go on his own focusing on the technology side. He was recently on a panel with two other highly successful commercial hydroponics "farmers" and they did an excellent panel he sent me the link to watch. With the marijuana industry become a massive market, I assume this will drive the cost of lighting, nutrients and all the hardware and supplies down to help make a better business case.
On the tech side for prices I hope so. But I do know that in that industry the lighting requirements are a lot more intense (and expensive) than what is needed for lettuce and things like that. The good thing about my outside system, the cost is relatively lower since it's all parts from the local hardware store and the Sun powers the rest :-)