RGray5801

I am new to this program but I am loving it so far. I have one question though. Why are coins such as Silver eagle proof coins listed only as bullion value. A 2015 W silver proof coin is listed with a bullion value of $15.49. But if I want to buy one it will cost me at least $40.00. The selling price is much higher then the bullion value. I am probable missing something. Thank you.