It's hard to say what a rifle worth. Everybody has a different opinion on value. How bad do you want to buy it? - How bad does he need to sell it?
The Browning SS is typically a shooter right out of the box. In the "less exotic" calibers, they were going for $600 - $700 a few years ago. Today, not sure of price. I'd check on gunbroker, etc. and look at actual sales - not wishful asking prices. I would expect used rifles would go for $100 to $150 less. All of the WSSM are slowing going away. There is little, if any support, from the mfg's today. I'm not even sure if any still make a rifle chambered in the WSSM. When I checked a few years ago, Winchester has stopped making them and Browning was only turning out a few. The action is unique to the WSSM, so I'm not sure how easy it would be to chamber it into something else. Good Luck.