There is often good advice and discussion in this forum about cars on TM, but obviously when someone is asking silly money ($30k) for an e39 540i people are going to have a laugh. Its human nature really, and will happen on any forum. The problem here is that there are more and more cars worth a laugh on TM, so the laughs are almost constant.
Maybe one stickied thread for TM Laughs, where they can all be lumped together, and then separate threads for cars actually worthy of a discussion. Thats how most other forums deal with it.