Pawn shops margin comes from buying products cheaply from desperate folks and reselling them at a premium where possible. If you are only buying than you can treat a pawn shop like a thrift store with the major difference being there possibility of price flexibility. If you limit your purchases to items whose value you are knowledgeable about you can secure decent bargains especially if you have any charisma and can negotiate.
If you go in for instance with no knowledge of jewelry and just pay their asking price for a random ring you stand a high chance of not being a great value.