If actors were paid on a tears-per-episode basis, the cast of Grey's Anatomy would be the richest people on TV. Ellen Pompeo, Patrick Dempsey and Sandra Oh are among the show's stars who reportedly pull down $200,000 or so per episode, and going into Season 8 some of them are going to be up for new contracts.
However, those on Grey's who want to come back could be hurt by the precedent set by ER. As an audience, we're used to TV doctors and nurses coming and going, and a good medical drama can keep the stories compelling even with a rotating cast. That gives the producers some leverage if Pompeo and her castmates want a boatload of cash.