Ask him for another quote from another garage so you can compare. You dont say what type or age of car you hit.Is it a newish car or an old banger. If a panel has to be replaced this quote would be cheap. Even if the dent can be fixed you will probably find that the whole side of the car will be re-sprayed to get a good colour match.
If you were at fault you may just have to grin and bare it. Depends whether you want to involve the insurance company and risk the increased costs through loss of NCB