Macbook Trade-in failure

I recently got a new Macbook Air, and sent in my 2year old Macbook for a trade-in valued at $600. The machine was clean, and had no damage at all. The shell was clean, no scratches or dents. Mailed it in with the very sturdy box Apple provided.

I got a notice that they were dropping my trade-in to $150 because of "dents over 5mm." It's dented now all right. There are two gouges on the bottom, and it came back covered in detritus. Not the shell, the inside. The screen and keyboard are covered in what looks like sawdust.

I had a bad feeling when I saw the Crystal Lake address it was heading to, and I wish I had taken it directly to an Apple store for trade-in. I doubt I'll get any relief if I walk into one with it now, it looks like crap and I can't prove they did it. I doubt I'm the only one they are screwing over with this trade-in "evaluation."

Two things:

1) learn from my mistake, don't do a mail-in trade-in.

2) does anyone know who I can contact regarding the trade-in program?