Large numbers have already been communicated about spending and trade of virtual goods in virtual reality worlds as it happened in the article Virtual Goods are a Billion Dollar Market about the asian market. Now Linden Lab, the company running Second Life, told that the volume of all time trade within the community has reached 1billion dollar.
Some time ago Second Life had a lot of press coverage accompanied by hype and disappointment. This is what makes these up to date figures most interesting. People do spend 100 minutes per session on average at the community and spend 50 million each month in user to user transactions. Further facts are available by the following article.