I was one of the people that you emailed about this deal, comicnut, if I recall correctly. I had done two or three different deals with Wilhelm a few years back, trading GA books for GA books. The deals we did ended up fine, but everything was set before books were exchanged as to what exactly was being traded for what.
If I recall correctly (and that's not a given certainly), the deal you're describing wasn't completely set but was conditioned upon a grading evaluation or something like that. Something like if it was x grade these books were in play, but if it was y grade, then it would be different. It wasn't my affair, so I didn't pay much attention. Anyway, that did give me some pause when you emailed me asking about Wilhelm, the part about sending comics without having a specific set deal in mind beforehand.
One thing I noticed about Wilhelm is that he overgrades by at least a point, so that must be taken into account if you're dealing with him. He does seem to have a fantastic GA collection, however.
Sorry to hear your deal didn't work out, and that you weren't treated fairly.