Condition is everything. Folks ask big prices because the 3" tube is a hot item at the moment with the masses, having been appreciated in the past mostly by those who carry and actually shoot their guns.
As such, many are over priced which have not been well cared for.
It's worth whatever you can get someone to pay. To me it is not a $500 gun unless it was in as new condition with box and papers. I know folks ask and get more depending on location and how bad someone has convinced themselves they want one. YMMV