1 Headway cell of 3.3V 15Ah, cost 20USD, it 2.475W per 1$
the Lipo that you show me it the most cheapest on HobbyKing, other Li-Poly battery cost 20-30% Higher,
but it i compare the deal that you show me, it 14.8V 5Ah, and cost 22.6USD, that is 3.27W per 1$.
so you need to pay 1.3 times more for LifePO4 compare to Li-Poly,
and get 4 times more lifetime and more safety technology.
and if we compare to average Li-poly battery cost, we can find 10-15% price different only.
now i happy with my AGM battery, i have 1 year so save money for Li-Poly or LifePO4, until the AGM will die.