The value of a silver 50-cent coin depends on the date of the coin, the mint where it was produced and the condition of the coin. In general, the rarer the coin and the better its condition, the more it will be worth.
In general, silver half-dollar coins are worth about $6 as of 2015 due to the current price of silver. However, some coins may sell for more because of their collectible value. For example, an 1895 Barber half-dollar in extremely good condition might sell for as much as $155. The image on the face identifies which type of silver half-dollar the coin is.