You could use second hand packs from racers who balanced/ discharged them properly. They last a long time for me and are pretty stable because of the previous care. (Racers often sell/give their used packs to the lhs.)
Or, you could snag the occasional deal. Now that many people are entering the world of lipo, your lhs may have new matched packs collecting dust. Look around and try to haggle with them since they're slightly out-dated and the lhs probably will have trouble selling them.
For instance, yesterday while I was at my lhs, I was looking around. I saw two matched 7 cell gp 3300 packs, assembled in sxs form. Price tag: 140 for both, 70 for one. (Meant for the emaxx, or any truck that took two batteries.) I've seen that pack for atleast 6 visits, so I asked them if they would sell for cheaper. They were the last nimh packs of good quality they had (rest were venoms
), all else was lipo. 100 for both, even, if I paid in cash.
So just try to look around. If all else fails, spc makes great ener-g packs, matched. (4600 mah) But they're self discharging rate is horrid. Really high maintenance.