I bought mine about six years ago for $360.
That being said, the prices of revolvers have increased quite dramatically over the past 5-10 years as the inexpensive police trade-ins have dried up. This is particularly acute with S&W K-Frame Magnums as they are no longer produced (the M66 was the last to go being discontinued in 2005). In my area, a used but not abused M66-2 with a 2 1/2" barrel, aftermarket stocks, and no box or papers would be priced fairly at $500 with a price as high as $600 not being entirely unreasonable for a particularly nice specimen.