Like kaosu04 said, CGG Sebbies do get a bit higher price. The BG42 is what will add the most value, though. From the recent BG42 sales I've seen on BF, $500 is probably average or even a bit low, especially if it really is NIB. That means you should get the birth certificate, box, wrench, etc. Then, if it's a BG42 "regular" Sebenza rather than "Classic", that's even better to most of the serious BG42 collectors.