At NYCC, Herb had Wolverine sketches on a large size paper, I really do not know what size it was but much bigger than a sheet of paper, for sale for $90.00. However, when I spoke with his representative before the show about getting a sketch done on a blank I was quoted as $150.00 per character for pencil and ink and another $100.00 to have it colored. No backgrounds.
According to: http://www.boblayton.com/commission.htm Bob charges $150.00 for a single figure with a minimal background.
Also, you can go to Herb's commission site at: http://comicbook-art.com/herbtrimpe.htm
I hope this helps at least somewhat.