I was told before that administration fee is for the cleaning, sampooing, tune-up of a used car. As I bought my taurus, I asked the dealer to waive the admin fee $250. They insisted and explained how reasonable it was to charge it. I told them - "I don't care whether it's reasonable or not, and I just want to pay the cofirmed price ONLY for the car. Don't mention others if you want to sell it." Then, the manager called me - "You have to pay for the admin fee $250, but we could reduce $250 from the car price." Heee... that's what I wanted.
It depends on whether you really care about the $400. Anyway, my taurus runs good and I like it. Good luck!