So if you break that down:
$50 an hr labor x 6hrs = $300. Give him a $100 for materials used and you have your $400. Doesn't sound too far off to me.
I sent all my alluminum trim (grille, headlight rings, trunk finish panel, and trim down both sides) of my `66 Belvedere II to King of Trim for an estimate. Just like body work, nobody is going to give you an estimate without seeing the items 1st hand. Lots of trust in shipping off your trim pieces, I know. I was given an estimate of $2,700 to strip annodizing, knock out dings, sand, polish, re-annodize, paint all argent silver and black back in...that was 3 years ago. The parts I had where good cores to start with (not a lot of sand pitting or dings). I had them do the work. Turn around time was about 6 weeks and I did send the finish panel & side trim back for re-paint. 1st attempt looked like it was masked off by a grade-schooler. 2nd time it looked great. Even though it took a while (and I had some 'do-overs') I would use them again. Unfortunately, I was not given an itemized receipt, just a total price.