h2o, according to one local PADI instructor: "The TDI nitrox course with two dives at USD250 should be on the right prize range. Normally, a nitrox course is between USD175 to USD250 depending on the location. Subic is popular for nitrox and other technical-related diving."
He added that his shop in Anilao, Batangas has a promo for PADI EAN (nitrox) course at USD175 per participant. "It also includes 2 dives and participant manual with certification upon completing the course. Course duration is only for one day."
I'll PM you his contact details in the interest of research