Depends on the color of your car. If you have E9 ( laser red metallic ) then yeah 400 sounds about right. It cost 500 to paint the cowl hood on my 00GT because the paint is a multi stage and has to be blended into everything that painted around the hood. Also keep in mind that most hoods will need to be blended a little into the fenders, that alone will cost $$$ cause of the prep work and time. Did you by chance get that quote in writing? or a verbal?
I never accept a verbal quote, especially on paint work, because 9 times out of 10 they will try to squeeze you for more money.
E9 is a hard color to paint so ive heard. I got into a little fender bender with my 00 GT and the guy at the body shop offered to repaint the whole car for 500.00 additional bucks, because it would be to difficult to blend everything. My buddy does paint work and a few other tought colors are : true blue metallic, dark shadow grey, and tropic green.