he is only buying 5% of the shares...he still needs another 5% to take control. So he buys these shares at 2.15...there is nothing saying he buys the rest at a higher price. This does not set a floor or ceiling price.
I think Mel and Malone know exactly how this is going to play out. Mel (by his silence) is trying to stand out of the way without upsetting the shareholders, and Malone is trying to get Sirius as cheaply as possible. It is inevitable that Liberty will get Sirius, spin it off, and make money. Mel just needs to find a way to exit gracefully.