Brake Master Cylinder problems of the 2007 Mitsubishi Galant

I purchased my 2007 Mitsubishi Galant on April 28, 2007. After about 7000 miles, my brakes started pulsating. I took a day off work to return to the dealer and have them fix this problem. The service department decided to just re-surface the rotors and send me on my way. About 7,000 miles later it happened again. . . So back to the dealership I went again and once again, they decided to resurface my rotors. . Now of coarse at 22,000 miles on my vehicle, my break light has been coming on with the pulsation back and my brake pedal now continues to move toward the floor when at a complete stop. So back to the dealership again only to be told that my master cylinder & brake booster are leaking and they will replace the faulty parts but that my rotors are too low to resurface again and that I will have to spend about $400. 00 out of my own pocket to replace them. . . There is obviously a problem with this brake system and I believe the rotors should have been replaced under warranty the first time or even the second time the pulsating happened.