In "About" 70% condition, the value would be "Around" $300 to $350.
Due to the hand labor and the EPA regulations, gun bluing has gotten expensive.
The going price starts around $125.00, and WAY to many of the people doing it are hacks that will over-polish the gun and ruin it.
GOOD gun re-finishers don't work cheap, and nothing looks worse than a fine old gun that some ham-handed polisher rounded off all the sharp edges and dished-out the holes.
So, you can have CHEAP, or you can have RIGHT.
Here's some places that offer re-bluing:
www.fordsguns.com/ (VERY GOOD)
www.apwcogan.com/Greetings.htm (GREAT)
www.apwcogan.com/Greetings.htm (About as cheap as you're going to find, but still be "OK', not great).
There are plenty of other places, do a Google search fro gun bluing or gun re-finishing.
Note that the few locals that still do bluing are typically hacks. This is simply because they only fire up the tanks once in a while, and they don't develop the necessary polishing skills.