Greetings, so now that VST's are in reason, one really nice thing is that many of them are transferrable as opposed to rack extensions... One of the great door openers for me leaving reason and discovering KVR a few years ago was trading VST's second hand. If you discover that you're not using a plugin, you can just trade with someone for something you want, keeping your plugin folder clean and free of bloat while getting stuff you want instead.
So that said, KVR has an awesome reputation system in place. That + the fact that buyers can dispute/recall payments in paypal if the other party doesn't deliver means that it's relatively safe to buy and sell, as long as you look up the sellers reputation on KVR first. What's the current policy of posting for sale threads here, where do they go and so forth? Is there any plans to start a Marketplace section here @ ReasonTalk? It might be a great addition. Otherwise I would recomend you guys to read up on the marketplace over at KVR, its one of the best things about KVR imo.