I sold my GBLE for, I think it was 12250. It had a killer topper and the after market flipper post <- highly recommended. 11,500 is an amazing price for this pin, sooo much fun to play and the rreverse flipper action on mass hysteria is a blast.
I personally would take the game off the market or look for a trade. I had trouble getting a fair price for my MMr. I believe timing has everything to do with it and lowering your price by a few hundred will not encourage someone to buy a pin for 10+k. Then one day some one will come along who really wants a GBLE and will give you a fair price for it. My 2 cents...