Assuming you are talking about a Browning double-barrel Citori (NOT a semi-automatic), you could get $500-600 for one in worn, scratched condition, and $800-1000 for one in near new condition. Subtract $100-200 for an older model without interchangeable chokes.
Browning Citori 12 gage over and under & a Browning Goldtrigger Light Twelve: How much are they worth?
50-650 usd
100-10000 USD depending on specifics.
100-500 USD
It's only worth what a buyer is prepared to pay !!
100-1000 usd
50-500 USD or OS
10-1000 usd
100-1000 usd
100-1000 usd
100-1000 USD or so
100-1000 USD and up depending on specifics