Asking in the D700 forum would probably get some informed opinions of what it would cost to replace the shutter assembly or whatever is the source of the problem. $500 for a D700 is too good to pass up if you have the lenses but is a questionable deal if needing to replace a current collection of DX lenses with FX lenses. That is where the real investment in photography is. Bodies are cheap, lens collections are serious investments. I would guess the average lens investment for amateur photographers shooting FX is about $10,000 unless they are BIF shooters which then increases a lot. A wild guess for a shutter replacement would be $450-500.. If you have DX lenses you like now and shoot sports or wildlife you might prefer to stay with DX and currently the best DX camera on the market is the D7100. If portraits, landscape, low light and not printing large are more your thing, the D700 would be tempting.