This post describes a possible way to manage selling electric Husky gear where an item bundled with battery and charger is cheaper than buying 3 items (unit + battery + charger) separately.

The brute force way to do this manually is to fiddle with unit invoice everytime you sell one in c9 until you land on correct price.

C9 potentially provides an easier option, by bundling the battery + charger into a part kit that is already discounted will save time with subsequent unit sales.

Consider a Hedge Trimmer.

The idea is we add a part with part number : 136LIHD45KIT that contains the 2 spare parts which are discounted to $250. This is achieved using part kits in c9. See following page on how to do this bit: http://c8software.com.au/wp/2015/05/how-to-create-a-spare-parts-kit/

You end up with a kit like this. (Ignore the Pink,  just Barney test setup, couldn't be bothered trying to do this in a non-test type setup)

Now, when you sell a Hedge trimmer, for kit , you key in part 136LIHD45KIT and it will bring in the components at correct price discounting.