Well if we assume 5M tablets made, and Kindle cost is estimated at $205 then selling out Playbooks in a firesale at $99 (known price point where even pets will buy an Android tablet) you get 5M (total) - (7. sold) = 4.3 * $106 per tablet loss = $455M (solving for X would give you $113 loss per tablet or $485M.

I've talked with Quanta before and I don't think they would have taken on the project without a 5M commitment, hence my guess at the number of playbooks made.