What are Browning shotguns worth over under 12 g and 20 g barrel sets?

This is like asking, "What's my car worth?" It cannot be answered without more information. Ask your question again with more detail. The prices of Browning shotguns vary greatly depending on the year it was manufactured, the condition it is in, the model, the gauge, and the type of action. over &under are the most pricey then auto loaders then pumps are the low end