Art Day: Paulo Siquiera commission

Well, I got my Paulo Siquiera Spidey saving Norah Winters commission today. As the scan I got looks great, the art is great. I am disappointed though, because I paid $420 for an inked 11x17 cover quality commission with 2-3 characters. What I got was an inked 11x14 high quality commission with 2-3 characters. The rep said he had no intentions of short-changing me, and didn't think anything about the piece being 11x14. Paulo's site lists 11x17. 99% of artists have a completely different pricing structure for 11x14 vs 11x17. He said I can send it back for a refund, but I am not going to do that. I like the art, but I don't feel like it is a cover quality piece because it doesn't 'look' like a cover due to the size. I waited a pretty long time for this, and I hope eventually the size of the piece will not bother me.