Still, I have to admit that if a 13x13x13 ever came out, I would want very much to own one, and I would probably be willing to pay pretty much to have it. I'd want to try to BLD it, even if that took all day. (Quick calculation [I hope I did it right] gave 866 pieces, which would be approximately equivalent to 4 7x7x7s! I'd guess that would take 8 or 9 hours on the first attempt.)
Lol, with 30 kinds of centers, 6 of edges and 1 of corners, that would be really difficult. But still it may be a problem to turn the correct inner layer, with 13 layers.