There is a significant cost, to the tune of $32B in this case. The spectrum they purchase is far cheaper than this - estimates for the upcoming FCC incentive a

There is a significant cost, to the tune of $32B in this case. The spectrum they purchase is far cheaper than this - estimates for the upcoming FCC incentive auction put each winner around $15B for a 10MHz up/down slice. Besides, if you put a spectrum block back up for sale, wouldn't that help AT&T and Verizon control more spectrum since they'd be in the best position to buy the freshly freed spectrum.