Using Skype is an excellent way of learning and teaching. It certainly saves spending unnecessary time and money travelling. The text box on Skype is an excellent means of showing corrections without the student having to spend time making notes as, unlike when using a whiteboard, the writing is saved in Skype after the lesson is finished.
I can also see what the student is writing without having to look over their shoulder as the text is on my screen. The sound is generally very clear these days and it is easy to discuss pictures and do speaking exercises, again I can write feedback in the text box and we can discuss it after the speaking exercise is over.
Cost per lesson: £20/hour