hmm, powered by an arbitrary high current DC power source... Looks like lithium batteries are still too esoteric and specialized to use without setting up an electronics lab.

I got mine for $24, paired with a 6 amp laptop charger, it's quite good. The functionality they packed into it is impressive.

(anyway)
I lump all of these chargers together because they appear to use the same core software/hardware package. The menu/info display screens are identical (though the color of the 16x2 character display varies) and they all have four functionally identical buttons lined up under said display. The functional specs also have very little variation.
Personally, I bought a "Supermate DC6" through hobbypartz.com a month or so ago. While adding a cooling fan, I poked around a bit and found the controller chip: An SMT ATMEGA168 tucked away under the LCD display, though some effort had been made to scratch off the numbering. An unused pin header was also apparent, which might be left over from programming (I didn't try to follow the traces to confirm). If these chargers are all as internally similar as i suspect they are, they could be interesting hacking fodder. Throw an Arduino bootloader in there (or not if you're hardcore like that ^_^) and write your own charging software.

There are a dozen or so varieties of this charger out there, sold under a variety of brand names at a wide range of price points (this is about mid-pack). The case design varies (overall size, cooling fins, fan or no fan and such), as do the power options (~12VDC with no AC adapter, 12VDC with adapter included, 12VDC adapter integrated into the case, etc). Some units include additional battery connector adapters (Tamiya, Deans, servo-style connectors for TX packs, receiver battery pack type connectors, glow-plug starter, etc). Some have integrated multi-cell lipo connectors (as above) where others have a single socket with an external adapter. Some include a temperature probe and a few even have a mini-USB port on the side of the charger, or include a USB adapter cable to log data to a PC.
(character limits? really? how about a click-to-expand-comment link?)

I know that a company's main source of income is from the products they sell (:D) but you can buy this charger from HobbyKing.com for $24 dollars apiece. I imagine that the price will go down as your supplier gets to know you but I'd rethink my pricing. Again, I know its hard to make money (especially in times like these) if you don't sell for a profit.
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7028