So, ha, after deciding there was no way for me to have any idea who was buying what, or how much of anything was selling (mostly useful so I knew if something just wasn't selling so I could not bother with it) unless I was logged in at the time to see the little message, I found the transaction history. Joy! It's pretty awesome and useful, and something I never would have found without seeing another vendor's "how to give no transfer items as gifts" sign. I'm pretty blown out of the water. Over 150 things!
And because I totally already had to go hunting for how I found it, in SL, World->Account History sends a message to your trusty web browser of choice to load the page.