In my experience, people almost never use Skype. They use QQ or other programs.

But efforts to learn a language individually are likely to suffer from a couple disadvantages, relative to being in a class. First, classmates can practice new material on each other. Second, economies of scale apply: It's much more time-consuming for a teacher (and therefore, more expensive for students) to have ten one-on-one lessons than to have a single one-on-ten lesson.