They'll also make a loss with this shipment even though they won't sell them at $99 again. I think this is just to build more Web OS customers so they can open source, licence or sell Web OS and say "we have this many customers".
they bought palm for $1.8billion and packaged up a few hundred million in a few product launches. If they want to sell palm at a profit or break even, it might be really important to add 1-5 million users even if there is a $100 loss per device.