Still, costing around 19.99$ for the users a total of 3 million copies were sold in the first four days. Operating system before Mountain Lion was always purchased, however, after the Mountain Lion all the versions were sold for free and it was the last paid upgrade. Mountain Lion was the start of macOS being sold free of cost as all of the successors of Mountain Lion were free of cost. It was released on Jon Mac App Store and was purchased around 19.99$. This change has brought Apple the option to release updates every year instead of their traditional every two years or so. As, Apple has released the operating system with the only available only on the Mac App Store.
The goal behind the operating system was to create an OS with better management and synchronizing between different Apple products. Mac OS X Mountain Lion 10.8 is the ninth major release of the OS family.