I bought my 125 gallon brand new from petsmart for $320 with glass top and lights... then the stand for $20 more. That should give you an idea. I believe petsmart sells the 120 gallon for just about the same price. Depends on how hard larger tanks are to come across in your area I suppose. I jumped on the 125 gallon I got. I can't hardly find anything in the papers around here.
125gallon - 3 Giant Danios - 1 7" Jack Dempsey - 1 5˝" Green Terror - 1 9" Lutino Oscar
65RR - SW - 30g Sump w/fuge - 40lbs MI LR 30lbs Base - 4-5"Sand Bed - 2 false black perculas, 1 six line wrasse, 1 peppermint shrimp, 6 zebra hermits, 6 blue leg hermits, 6 nassarius snails, 6 astrea snails