For SEMA tickets, check craigslist.org .. i get them every year from this guy who advertises on the site. He sells extra badges from companies exhibiting at the show.
I got them for $60 each.
I think it's a fair price considering that SEMA isn't open to the public and the passes are good for everyday of the show.
Here's the link to his post:
http://lasvegas.craigslist.org/tix/2585595985.html
Or just go on craigslist.org and search "SEMA"