Depends, work it out.
A brake test SHOULD only cost the time.
Work it out on $100 per hour for an engineer.
Remember they won't break the law either.
My brake test is costing $200, as the nearest 110kph country road is about 40mins away.
So 40mins each way, plus time for the brake test = 2hrs = $200.
Ask them what they plan to do for the brake test.
My engineer is doing 2 successive 110kph emergency stops, and a 35kph handbrake test.
So it will take him about 10mins to complete.
Its the getting there and back thats the killer.
If they are charging $400 for a 10 minute test, that will take them 10 mins from the time you drop the car off, its a ripoff.