You can't really fault the dude for trying. I mean, you are right that they've appreciated greatly over the years, and that it's very unlikely that someone is just going to post on here selling their 1st Gen 73 Model T for $400. However, there's no point in being crass about it. I know when I found this forum I was anxious to find similar dream-deals, and I've made some killer scores through this site, whether directly, or through people posting links to other sites.
Anyhow, I'm one of those people who sucked it up and bought via eBay. I can afford to, so I did, but as far as people posting their gear for cheap, it happens. Believe me. I've seen Sunn cabs going for $100 CAD. Hell, I just bought an Acoustic 406 for $250. I've scored incredible deals by being persistent in checking around, and hopefully this dude will, too.
My point is, don't pick on someone for giving something a fair shot. We've all been there, so have heart dude. Hopefully this person will appreciate that this forum is full of knowledgeable folks, and will make the most of what they've stumbled across.