With your setup, how much water are using now? Do you see a significant savings in water/cleaning solution? I ask because using a plastic tub to accommodate the manifold looks much wider than some of the bucket solutions out there and as far as I understand the pump needs a minimum level of water to run safely. I am by no means looking to save the world here, but I wouldnt mind saving some $$$ on PBW...
I don't know how much less water, cleaner and sanitizer I'm using now but it's certainly less than I was using.
I don't think you can justify the system based on savings on chemicals/cleaners/sanitizers. I built the system for the convenience of being able to have the system do the cleaning chores for me while I do other things.
I did recently find a smaller tub which fits the manifold perfectly so I am using less water and products now. I will post a pic when I get more time.