When the hairline has just been put in, it looks high up, once the hair grows, it'll look at least a cm lower unless you brush your hair back exposing the line.
The doctor may feel that you may have aggressive loss in the future & wants to reserve grafts. He could easily add another 1k, at the end of the day it's more money for him.
The pre-op would have showed you where the line was going to be placed anyway.