what I've learned about GC is:
"name your price and walk the hell out if they don't play ball." Now, something crazy is obviously not possible (like half off), but I always get things knocked down by a hundred or so, you did alright.
The trick to G.A.S.ing is to not let the GAS throw your judgement. If your price can't be met, walk the heck out. I actually have walked out as I find they don't budge much on:
* Top-line Fenders
* Top-line Gibsons
* Top-line Music Mans
That is just my experience.