If I was selling this service $400 is about what I would charge for a clearcoat. That's based on 3-4 coats (sanding/prep in between) and no touch-ups. The average pf is getting roughly $50-$75 worth of materials alone (2-part auto clear, reducer, sandpaper and other consumables). Tack on about 5-7 hrs of labour and you're roughly at $50-$70/hr. For a skilled service on a freelance basis that sounds about right.
I was charging a bit less when I was just learning, but I think most guys who do decent work are at this rate or higher.