Don't know exactly what formula dealer use. But it base on the spot price of an oz. of .999 silver. Silver coins are only 90 per cent silver. $1 worth of silver coins is .70-.72 oz. so based if spot price of silver is $10.00 x .90 equals $9.00 x .70 or .72. $1 silver coins would be $6.30 - $6.48. Of course silver is betwen $11 and $12 currently was $11.70 on Sep 1.