Hi there, we don't mind people selling things but it is better if you do an introduction to tell us who you are, what you do, that sort of thing. We do mind strangers turning up with goods to sell without getting to know us first. If you are just here to sell the airbrush I would recommend you post it on ebay.
To help you with the costs, second hand (regardless of state) is around 1/2 price unless it's something special. What I mean is "rare, hard to find..." These are still available so a price tag around the $200 US. That would be in excellent working order with all parts undamaged.
Thanks, Mark