You can build a very high quality lighting system with NiMH batteries for about $110, including a smart charger. If you want to use a sealed lead acid battery then you can lower the cost to about $75. You can eve get by with spending as little as $40 for a very capable single headlamp system. The commercial lighting manufacturers charge very high prices for their NiMH systems, even though NiMH batteries have plunged in price as they have become a consumer item used in digital cameras. A 24AH NiMH battery pack will cost you less than $15 (ten 2000 mAH AA cells and a ten cell battery holder). What drives up the price of homebuilt systems are the niggling bits of hardware, connectors, battery holders, and switches; items that are very cheap in production quantities, but very costly when you buy individual quantities and have to pay shipping (many of these pieces are available only via mail-order, and the shipping costs can be $5 on a $1 item). On the other hand, the commercially available lighting systems charge very high prices for their NiMH battery models, even though NiMH batteries are now very cheap.