I'm actually really surprised at how many people are just assuming the OP was ripped off because they did the job themselves cheaper, and didn't have to do it until longer.
The OP mentioned that they owned the car brand new... that's over 5 years. Also driven to work... so regularly.
I drive my car to work 5 days a week, and I work 14 miles each way from my house. I use the brakes five times each way: turning out/in to my street, 1 stop light before the highway, off/onto the ramp, in/out of the parking garage, and parking the car. That means My brakes make contact 10 times over 28 miles.
If you work 1 mile from house, but have stop lights, stop signs, school zones, and/or hills... you may hit brakes 40+ times each 2 mile trip. It isn't exactly impossible for brakes to wear down in 30k miles over 5 years of use.
Also, if it cost the same to have your brakes done at the dealer with OEM parts, you wouldn't be shopping online for coupons to spend 2 hours of your saturday working on brakes. I know, if it saves you a couple hundred bucks, sure. But here's the thing, and there's really no way around this:
OEM is not OEM. It may feel 95-99% like OEM, but it's not OEM. Some people get a peace of mind in knowing that a car has no excuse to not operate as expected because all the parts are made by the people who engineered the car. That peace of mind is baked into the price of OEM parts, and they usually ARE more expensive (particularly where "BMW" is the OM).
Bottom line, it's impossible for me or anyone else to really tell whether the brakes were in operating condition or were safe to drive without looking at them. $1,400 for a full OEM replacement of pads, rotors, and sensors is not irregular for what BMW dealers charge.