NBC has announced that they are seeking $425,000 for a 30-second advertising spot on “ER”s April 2 series finale. The medical drama, who is closing its doors after 15 seasons, is saying goodbye with a two-hour-long episode that features the show’s original stars, such as George Clooney, Noah Wyle, Julianna Margulies, Maura Tierney, Alex Kingston, Sherry Stringfield, Eriq La Salle, Anthony Edwards and other cast members. La Salle also directed a recent episode of the show, entitled The Family Man, in addition to making an appearance as his former “ER” character, Dr. Peter Benton. In previous seasons, “ER” asked $135,000 for an advertising spot and brings in a cumulative total…