Those two statements don't really go together when it comes to collectable airguns, or anything else really.
In my view, they only have a 'shootable' or 'parts' value as the refinishing and painting will have diminished any 'collectable' value.
I'm sure some one will come along and put a value against them, but without any photos it can only be a rough guide.
Not trying to put a downer on your friends guns, but originality is key in getting a good price for a collectable airgun or even a modern shooter.