They're wonderful little guns; accurate and reliable (as might be expected from something designed by John Browning). My nephew picked one up last year, and loves it to death.
Most of them I've seen were carried a whole lot more than they were used (Al Capone carried one), so they look bad but mechanically are sound.
If the bluing's about gone, that isn't surprising for something that may have hung around in some guy's pocket for forty or fifty years. How bad is the rust? If it's strictly surface rust instead of pitting, what you were quoted might be about right around here. Of course, I live in Southern California.