from a store like home depot you're looking at about 60$ just in plywood alone, then add the 2*4's, add the doors, time spent on the project, and finally using someones table saw the 120 is a pretty good price.
If you didn't want to cover the stand with wood and doors and just make a frame for the tank it would be more around 20$, but it wouldn't be pretty.
by the way I have a frame only stand.