I agree with code red. Unless your trying to factor how much water your using into the equation, after the initial $50-100 for the set up it rarely costs me more than $20 a year for my fish (except when I have to add new tanks LOL). If you get a regular sized can of pellets, a thing or two of frozen foods, and maybe one can of freeze dried something or others plus a carton of aquarium salt.. it will cost you about $10-15 and can easily last a year or more depending on how much you feed.
I also feed my guys live brine shrimp weekly as a treat which costs $1 a scoop at my LFS. Hopefully I can set up a DIY after I get rid of my fry and just raise my own brine.