It seems to be used when people sell new guns where the margins are very tight. It does stop people shopping by price and avoids cut throat discounting to almost nothing. It also can mean that a shop has an inventory of stuff which is under retail for one reason or another but does not want to advertise that widely.
When selling used guns, I personally do not like it as many people shop by budget. They will not waste your time or theirs calling about a 5,000 gun if they only have 3,000 to spend. Seems sensible.
Sometimes a gun may be in on commission and the vendor does not want the price advertised widely but will talk to serious enquirers. As I say, I thin the policy has more downside than upside and avoid it when possible, which is almost all the time.
