I think spectrum is quite a bit more expensive than that. Qualcomm recently sold a spectrum block to ATT for nearly $2 billion. Granted it was probably a more desirable block (lower 700 Mhz) than most others.
Yeah, that's a good point. But even a billion dollars wouldn't put it out of their price range. I'd also imagine they could drum up serious public support by offering to give everyone free cell service, and maybe squeak out a legislative discount.