True, its not the money reason, its the fact that they dont output as high a voltage/amps whatever it is, as is needed constantly so will cause problems with your kit
i use rechargable AAs in my Reloader and its fine - lasts about 4 trainings/events - due to the reloader being able to run on 4 AAs the lower output from recharables it pretty much compensated
i use an old 9v rechargeable in my ego grip frame for training, i just recharge it every saturday night before i go. alwaysa lasts all day no problems.
i use a fresh decent battery for anything important though