Keep in mind that in electronics manufacturing, the majority of the cost is in the parts. The circuit board will have been custom designed and produced in batches ahead of the actual assembly, so the cost for the additional boards is completely sunk(already paid for). The other components such as display, processor, and memory have some value on the secondary market, but have already been purchased with commitment for a large volume to minimize cost. If HP sells these components on the secondary market, they will receive less than what they paid for them.
I would guess that HP is still going to be losing some additional cost in manufacturing additional tablets, but it won't be anywhere near the $200 difference. In return, they increase the amount of tablets available run WebOs which they are still hoping to be able to license to other manufacturers.
The only thing that doesn't make much sense are the statements that these tablets will be available in a few weeks. Most items ship from China via ship, and a basic rule of thumb is usually a month from leaving a production line to being available at a warehouse for shipments to and from China. Actual time on the sea is less than this, but containers must be loaded in a container, trucked to port, wait for the scheduled ship, unloaded (and make it through customs), and transported to HP. For this reason, I am suspicious that some of these tablets that will be becoming available may have been already produced and have been moving through the system. While it is possible HP chose to stop production well before they started announcing the bargain price for the tablets, it is hard to keep a secret in Chinese manufacturing plants as Apple finds out often.
