I am just reporting a ballpark figure from the data usage i get when actually using hangout for meetings on 4G on my phone.

That said at 3600s per hour 1GB/h would be 2.2Mb/s, which does not seem outrageous for a 8 people meeting

That wouldn't really be surprising if it's an HD video chat, especially when you consider that the communication would likely be bidirectional (unlike normal video streaming, which is one-directional).