The millage isn't really an indicator of when pads go back since you could drive a lot more highway miles and the pads could last longer vs. city driving. Also, OEM brake pads tend to not last as long. Have you had your brake warning light come on or are you hearing the squealing sound of the "alarm" from your pads? Most brake pads are 12mm so you've used 1/4 of it already. You can probably squeeze out another 5000 miles if you haven't already hit any alarms but that's up to you.

$750 does sound a bit steep but then you have a luxury line at a dealer so everything is more expensive. Are they changing the rotors too? I doubt that are. Anyway, again it's up to you. You can go much cheaper for just a pad change and machining rotors at a local shop and after market parts. Or hell, you can do it yourself. Then again, it's a new car and you have a warranty and such....