You have to compare it to something else. That is, can you get an
independent mechanic in your area to do it for less? Can you buy the
part and DIY? That's the only way to figure out if it's reasonable.

Sounds high, but it depends on what you need for parts. If you need
both rotors and calipers then it might not be too bad. OTOH, if you
only need pads, it's very steep. I generally find that most places
charge too much for brake work as the work is simple and it's mostly
plug-n-play these days - they are in and out in an hour. But, you'll
need to post more detail on what they estimated replacing and again,
perhaps consult another mechanic if you do not DIY.