If you're opening cartel packs you're doing it wrong. I sold them for over a million each. Of course now since undercutting is crazy they don't go for that anymore but on the flip side all the cool stuff is much cheaper.
I sold 13 packs for 1.1 million creds each. With the undercutting I was able to get a white crystal, throne, etc... For not even half of the creds I made from selling the packs.