best "premium" wordpress themes guys out there right now is WooThemes: http://www.woothemes.com
to be honest though this question is going to get you some very subjective answers
Premium suggests one thing to me - excellence. excellence/premium themes generally have a "premium" price tag as you are paying for what you are getting - theres no point getting angry about that, quite simply these developers invest there time and energy into developing these themes for our use, in many cases the time taken is in the hundreds of man hours - the developers have to recoup there costs some how
if you want a "cheap" theme then you dont want a premium theme, that said woothemes linked above does have some excellent themes that they provide for free.