Tesla -
If they sold you a defective product, and are only giving you a partial refund, it doesn't hurt to speak to your credit card company, and see if they can help you get back at least some of the "non-refundable shipping charges." Considering the product was defective from Day 1, you shouldn't have to pay $30 just to play Quality control for them.
I wonder what percentage of the AirPads are being sent back, and of those, how many are defective (as opposed to the customer just not liking the design or features of it).
I would make the assumption that all of the ones being sent back for replacements are defective (why request a replacement for a unit that is working perfectly?), and at least some of the ones being sent back for refund are, too (and the users just don't want to bother with another one).
I'm sure we will never see those numbers, but I wonder how successful of a move it was for them to have ventured into the Tablet arena.