$600 is a little high..i think $500 would be the average price for a single display tower. Most people would argue it since some find them on craigslist for at least $100-200, but $500 is an average price.
Never heard of trading cameras for display cases lol. But if you have no use for the camera then id say jump on it! Personally i hate cameras and just use my phone so if i could get a display for a camera...someone pinch me I'm dreaming!! Im sure this camera is professional and pricy so please don't be offended..lol
I'd say if you really really want it pay the $600. I say that because people are paying freakin $500 for cubes which are not even half the size of a full tower. $500 is a more realistic price tag for it but it depends on how bad you want it.