It would seem that so far Skype alone, on in the background, but not being actively used, uses approx 10mb per hour, speech call only, 25mb per hour, but video call uses between 300-500mb per hour. All that is assuming one's laptop isn't a 'supernode'. So if usage is 3hrs per day, 7 days a week and 4 weeks per month, the approx usage of bandwidth is 33gb
Our monthly limit is 'only' 20gb, which has always been more than enough and then some for surfing/streaming/downloading/uploading/anything and yet we are but mere amateurs in usage it would seem......
SHJ