A lot of whether Skype is "eating" traffic?

apparently you have enabled super-nodes

Windows Registry Editor Version 5.00
\r
[HKEY_LOCAL_MACHINE\\SOFTWARE\\Policies\\Skype]
\r
[HKEY_LOCAL_MACHINE\\SOFTWARE\\Policies\\Skype\\Phone]
"DisableSupernode"=dword:00000001

In simple:
\rOn average Skype uses 0-0.5 kilobytes/sec while idle.
\r
For calls — it is clear that in different ways. From 10 kbps usually, as a rule, not more than 30 kbps. For video calls is usually up to 70 kbps, although maybe all 300 to take if High Quality to include.

My sense is that much depends on whether the computer on which Skype is spinning the opportunity to listen to ports for connections from the outside and if there is, the width of the channel. Was very unpleasantly surprised after six months of use Skype 24/7 (and a couple of kilosymbols text messages) that have resulted in hundreds of kilobytes of traffic on the channel in 1 Mbit per provider Nate, when he came to account for traffic (at 1P per MB) on channel 10 Mbit with white IP in the same mode traffic exceeded the usual several (not one as I expected) orders. Appeal against a failed (that is, in principle, reasonable, but no harm in trying), since Skype only in "Emergency exit Skype, otherwise the cooperation will stop the" soap/telephone and if the collaboration is worth it :)

and despite how much you find.
talking to people on bad channels (up to Skype over gprs), it is not particularly a lot of eating.
\r
in General, it was somehow a gig for 4 hours in a conference 4-5 people. then the conference reached a half dozen, but I traffic is not considered.
and Yes, when 12-15 people in the conference my e7300 significantly slowed down.

You can put Netmeter and lock the current speed.

Mac OS. Watched the data flow during a call — In:15-35 kbps Out: 14-20 kbps