It's worth between $10 to $15 used.
About $30
100-550 or so
100-400
A center point scope would probably be better for an airgun considering it would be the most cost effective. A leapers or red dot scope is nice for combat and tactical operations because the illuminated dot allows for quick sighting in high adrenaline situations. I am assuming you are target shooting or hunting small animals with the airgun which is why a center point scope would be a good choice because it tends to be slightly more accurate for a much cheaper price.
100-425 or so
$55,000
45 or so
300-600 USD depending on exact configuration and condition. The scope doesn't really add any value.
Unknown caliber. Contact Ruger
There is modest collector interest in Mossberg rifles from that period. Value will depend on EXACT condition, and completeness (many had rear sights removed to add scope- replacing them is pricy.) Prices for very good, complete, range from about $125-200.
25-75 usd
Which one?