If you think about it, unless all services are donated, it is quite a few jobs. The money in the campaign might go to someone to design the postcards (for example), a four-color printing company which would order the paper stock from a paper company, and then employ an operator (like a pressman/oversized computer printing machine), and a binder if they are cut from oversize stock. Someone has to drive them or pick them up to be mailed, where they are sorted and then delivered to all the mailboxes or PO boxes. Multiply that times a number of candidates, and it's some work.
Folks can debate whether the money spent is worthwhile....