Since the launch of the BattleTag system back in 2011 players have been able to change theirs free only once. Many probably picked names they no longer wish to be known as or perhaps tied to the Blizzard game they were playing at the time but no longer play. Players have requested the ability to change their Tags more than once and today Blizzard have made that so.
It’s a welcome addition although the round figure of 10.00 seems a little arbitrary for an automated service. A case of sticky sausage fingers?