Batteries aren't expensive anymore:

ZIPPY Flightmax 5000mAh 5S1P 15C 578gr $42.95
ZIPPY Flightmax 5000mAh 5S1P 20C 586gr $55.70
ZIPPY Flightmax 5000mAh 5S1P 25C 628gr $66.08
ZIPPY Flightmax 5000mAh 5S1P 30C 650gr $54.85

Here's the ESC:
[link=http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=4691&Product_Name=TURNIG Y_Sentilon100A_HV_5-12S_BESC_(Ver4)]Turnigy 100A ESC[/link] $99.99

I bought bunch of these (same brand different cell counts and capacities) this past spring as a test. I puposely abused them (hot charges, overdischarge, etc.) and so far after about ~25 on each they are holding up great. For, literally, a third the cost of 'name-brand' packs I don't see a downside.