there is a valor requirement for buying champ commendations (50 valor)
it sucks. and you are still better/cheaper off buying the bags in long terms. Champ bags costs 800 commedations (calculated merc and wz together into wz only commanedations)
and 1 champ commendation is 120 wz commendations. 1 champ bag gives 7. buying 7 champ commendations with only wz comms would mean that you need 7x120=840 wz commendations. not to mention that a champ bag MAY give an unassembled item and, ofcourse, cash. and if need be centurion comms.