A number of classic commems circulated as half dollars and the Stone Mountain did tend to circulate quite a bit, probably due to its 1.31 million mintage. That mintage was massive considering most classic commems had a mintage under 100,000 and a large number were under 50,000. The mintage was only surpassed(barely) by the 1893 Columbian. The Stone Mountain commem can be easily found in VF-EF conditions for $30-50 and you can get an MS-64 example for around $100.