WHICH revolver?
Double action? Single Action? Prefer S&W over Ruger or vice versa? Or are you willing to gamble with a new Taurus?
The cheaper way to go is with a Ruger Super Blackhawk SA gun. New they are around $650 in blued. Used they seem to go anywhere from $450 to $550 depending on age.
Double Actions come in a variety of types. The main ones currently that I know of and woudl consider myself are the Ruger Redhawk, Super Redhawk and S&W 629. Taurus makes a couple of .44Mag revolvers as well but I've seen enough warranty issues to spend a little more and stick with Ruger or S&W.
For used you're likley going to spend from $600 to $900 depending on the model and make and condition. New guns are listed on some of the various dealer links at the top of the page for comparison.