Many things affect the price of a silver dollar, including its age, rarity and condition. Silver dollars are not priced solely on the current silver bullion price.
One of the top factors considered when determining the price and value of a silver dollar is the condition. The process of identifying its condition is called grading and should be done by a professional. Rare silver dollars-- meaning a minimal number of them have been made and are still in circulation-- are often priced higher. This is due to supply and demand. Experienced silver buyers know the rarest silver dollars and often offer top dollar for them.