Glad that you weighed in! We decided against a hydroponics system for several reasons, including that our planting patterns wouldn't work very well with a hydroponics system. Our heating and cooling (and humidity) systems are significantly less taxed with our current system as well. The in-built filters are more easily integrated with the rest of the system. The entire system as a whole weighs significantly less. We were working with an aquaponics research group a while back, and our current 2 foot by 2 foot by 26 inch system weighs less than the water that their 36 inch by 16 inch by ~6.5 inch unit used. While intermittent spray systems may consume less water, they also require more energy for the spray systems (in addition to the increased cooling and humidity regulation costs).

As for cost, I had a good (well-meant) laugh at the overestimation of the price. If only we had access to several billion in funding! I fear that you overestimate the price of a single unit by several zeroes. I can't tell you the exact price as we are negotiating the selling price with the space sector, but a full solution will be significantly, significantly less than that.

Edit: a word.