Oh, for sure lithium-ion batteries get really expensive when they get that big. On the positive side, EGO offers a 3 year warranty on their batteries, and my experience is that they generally last a lot longer than that. The real advantage in lithium-ion over SLA batteries is that they charge much faster, and in the case of EGO, the 7.5Ah (420Wh) battery recharges in just one hour. A comparable SLA battery would take at least 12 hours to recharge. Also, the lithium-ion battery weighs at least 20 lbs less.