Update: It looks like they got their wish... they will be getting $1 million per episode.
According to The Hollywood Reporter, it seems that continuation of production for The Big Bang Theory's eighth season was put on hold due to some contract concerns.
It was said that Jim Parsons (Sheldon), Haley Cuoco (Penny), and Johnny Galecki (Leonard) are requesting up to $1 million per episode, compared to their current $325,000. They were also said to be requesting a cut of the back-end profits.
Looks like they're pulling a "Friends" !