If you have a Mac, you’ve already paid for it. If you don’t have a Mac, it’s $30 for QuickTime Pro.
With QuickTime 7 you still had to upgrade to Pro on a Mac. OS X 10.6 comes with QuickTime X, for which there is no pro version, but it has more features than the old Player (including screen recording). If you want Pro on 10.6, you have to install QT7 and enter the Pro key.