Just a small deposit to start the process
Sprint is dying because their network remains slow as dialup even after applying all the 4G buzzwords. Somehow upgrading went well for other telcos. It also doesn't help they sold a lot of Sprint-branded defective phones on contracts and told their customers that they're SOL. (Thanks for that defective Galaxy S2, Sprint)
I don't think the US Government would allow Sprint to kill the best candidate to challenge Verizon and AT&T. Despite this, I'm sure T-Mobile wouldn't mind starting the paperwork for a small, non-refundable, $4 billion deposit.