What the used price is depends on the firearm, and where it is for sale. I know that new Colt Single Action Armys retail for around $1300-$1500, and at the shop I work at we had a used one for sale that was around $850, and another gunshop had a similar Colt for sale that wasn't in as good of a condition and it was for sale for around $1000. Another example I can think of are used Sig P299's (older models) compared to used XDs. New Sig P229's retail for around $900-$1000, but used older models sell for around $550-$650, and as for XDs they retail for around $600, but used ones sell for $450-$550.
"It's a gun you loaded on Sunday, and shot all week."
"If God didn't create man equal then Sam Colt had made them equal."
"Fast is fine, but accuracy is everything."