Update from the author
Having received a letter from a reader concerning my article on lithium-ion batteries, the price of batteries, and one of the website links that's not working, I too have noticed good deals are more difficult to find and the really good prices with free shipping are even harder to find. This has occurred because the US Postal Service has recently announced they will no longer accept Lithium Ion batteries and other items with lithium in them for shipment in US Mail. As a result, Ebay sellers have either raised prices and still offer free shipping, or raised both the price and the shipping since they are now forced to use higher cost shipping methods. The only thing I can recommend is to keep shopping. U.S sellers and overseas sellers have all been affected.
You can still build a pack for a lot less than those for sale bybattery advertisers.http://www.all-battery.com/4tenergyli-ion1865037v2600mahrechargeablebatterieswithinternalpcb.aspx
12 would cost $86.97 plus shippinghttp://www.ebay.com/itm/12x-18650-3-7V-5000mAh-Li-ion-Energy-White-Flashlight-Torch-Rechargeable-Battery-/150772118923?pt=US_Rechargeable_Batteries&hash=item231ab7f58b
12 would be 37.09 with free shipping but may not have the PCBhttp://www.batteryspace.com/Battery-holder-Li-Ion-18650-Battery-Holder-2S2P-With-2.6-long-20AWG.aspxBatteryspace.com
now offers the battery holder with the PCB built in. This will allow you to use any 18650 lithium Ion batteryavailable on the market without a PCB They are $15.95.
You can still build a pack for $12.36 for the batteries $15.95 for the holder or $28.31 each using the above two sources. Or you can get the Tenergy batteries and use the cheap battery boxes without
the PCB and build the packs for about $32.50 each.
Bear in mind things can change pretty fast. The battery sources I used in the article were correct when I wrote it.
Sorry about the bad news!!