Their was a thread here on Reef Central where people listed the cost per gallon in their setups.
I'm post #27 on there...
I came up with $16/gal on my 210 gal. I wasn't the lowest so it can be done cheaper than I did it still.
I'm sure that people can do it 'on the cheap'...but the average is much higher...
I have 80 fish... IF they averaged ONLY $50 each, that's $4Gs right there...and many of them are not $50!
With over 40 yrs in the hobby, I'd say easy 6 figures is where I'm at...especially when you include everything, like mods to the house and backup generators and etc, etc, etc.