I believe I paid some where in the neighborhood of $600 for my 36V 10Ah LiFePo4 through a reputable shop w/excellent customer service about a year and a half ago. I disremember the exact amount, I bought the motor, battery, controller, and a Cycle Analyst at the same time.

I would rather pay a little more, and deal with a reputable shop, than try to save a little money and buy a battery,charger ect. on the 'bay.