They're not purchasing them to send off to the troops? Are you sure? ;)
Our county Republican party bought a bunch of prepaid phones to use for phone banking in the last election because it was cheaper than having 20 phone lines turned on for the short time of the election cycle. There are legitimate reasons for buying lots of phones. Having said that, I don't mind the FBI checking it out. If it is legit, fine. If not, hang 'em.