I have talked to the extension agent here, however there has not been extensive research done on pasture and forage crops. Limited trials have been done in a replicated (clipped) scenario, but that is even pretty limited. I spoke with them again today and they might be willing to come out and plant some plots for a study, but I am not sure of what limitations there might be with that.
Water costs depend on what irrigation district you are in. For instance some are as low as $20/ac and others are as high as $140-150/ac. The one on the higher end is a pressurized delivery, but even at that I am not sure how well that pencils. Lots of hay and row crops in that water district. I would say the average is somewhere in the $40-50 range, but this is without power costs if you are not all flood. (There is the occasional property listing that shows "free water" from on farm wells, but they don't consider the lift of pumping the well let alone the thrust of the above ground pressurization)