Yes it does, because in addition to your own traffic, your line also has to support the traffic made by other people - with torrents, this means uploading to other people what you've been downloading.
I don't know exactly how much bandwidth Skype uses, but it has been the most reliable way of doing video-chats for me, even on the slow Internet connection I'm using.
Yeah, but in these use cases it's using a lot of traffic because the application of file transfer, and voice/video conversations use up a lot of bandwidth.
If we take, for example, an application like Bitcoin, it uses a minimal amount of data transfer because all it's doing is coordinating transactions and mining.
If take a simple use case like P2P text chat, would the bandwidth costs be all that bad compared to a cloud or client-server model?
I don't know exactly how much bandwidth Skype uses, but it has been the most reliable way of doing video-chats for me, even on the slow Internet connection I'm using.