How much is a 100 1997 Franklin quarter pound silver proof worth?

This a a 4 troy ounce ingot in a particularly pleasing form. The accurate answer is however much you can find a buyer willing to pay. The value of the material is only part of the total value, and fluctuates from minute to minute - as of the time I am responding to the question (spot at US $27.01), the silver content (124 grams or 4 troy ounces) is worth $108.04.

*Note that one fourth of a troy pound is approximately 93.4 grams (3 troy ounces). A troy pound is approximately 373 grams... 12 troy ounces. Silver is always measured and sold by TROY weight. This is actually a third of a pound of silver, for any that care...