The cost mainly depends on two things:
1. The cost of the harness (kit) as supplied by Christian (Shonky).
2. The shipping costs.
Both are not under my control, so I can't say much about those. The shipping cost highly depends on the weight of the harness, which I can't tell right now. I assume that harness + packing will be somewhere between 200 and 500gr (between 1/2 and 1 pound apporx.). If this is right, shipping costs from me to anywhere else won't be below 4$ and won't exceed 12$ as far as I can tell so far.

In my opinion, it all comes down to one thing: Do you want to have a harness with the original configuration at hand at any time (and thus probably not modify the original harness), or can you live with a modified one. If the latter is the case, you will probably not want the harness from me, because it will probably get damn close to 80$ (if not 100$) total. It all depends on the number of people wanting a custom harness though, as more people sharing the postage from AU to DE means a dramatic decrease in shipping costs. If multiple people from the US join to get one box from me and handle the (then internal to the US) distribution among them themselfs, shipping costs will decrease even more, which might bring the price down by a total of 10-15$ per harness (for shipping AU=DE=US-US, with = indicating combined shipment for multiple buyers).

cu,
sven