They make a profit because they buy stuff for around 75-85% below spot. For example they would give you like $9 +/- if you took a Morgan dollar in there to sell. Some of these shops dont sell to the public, they sell to a wholesale buyer and the rest just goes to a refiner. The one i frequent actually does sell to the public and those are the ones where you can somwtimes get lucky.. Usually these type places have a sign up that reads: WE BUY GOLD. They are mostly located in major cities though
Maybe they value social skills, good attitude and customer service over someone who's knowledgeable about coins. Idk why really, that is just what someone told me, they must not know too damn much, otherwise I wouldn't keep finding $80 & $100 coins for sale with a $20 price tag