anything less than $600 is few and far between, and a $600 shooter will have something wrong with it. Reblue, pitting, mismatched major parts, etc.
The $450 or $550 gun is getting harder to find. Not that it doesn't happen, $600 is a lot for most "average' pistols, so you offer $500 to a widow or guy at a yard sale and he might give you $75.00 back in change.
Ed