How much are 1999 silver dollar coins worth?

It depends on what you're referring to.

If your coin is a small (26 mm) dollar with a very unpleasant picture of Susan B. Anthony on the front and an eagle landing on the moon on the back, it's a regular circulation coin worth $1. In addition it's made of copper-nickel, not silver.

If your coin is large (38 mm) and has Miss Liberty in a walking pose on the front and the Words 1 oz silver on the back, it's an American Silver Eagle bullion coin containing 1 troy oz of .999 fineness silver. They technically are worth whatever the current quote is for silver You can find current price info for precious metals at: www.kitco.com/charts/livesilver.html (for silver) Be aware however that because of the increasing demand for silver, pure 1 troy oz coins and larger often sell for an additional premium on top of their metal value.