[whswhs]

I think the relevant rules are, first, that building a copy of the invention costs 20% of the retail price for parts, and takes half the time (p. 474, Production), and second, making the copy takes a Prototype roll with reduced penalties (p. 475, Prototype) and with reduced time and cost (pp. 476-477, Prototype).

You've already got the facilities and don't have to pay for them again. A Scrounging roll finds the needed items at very little cost; however, since you have already scrounged once, I would either (a) apply an extra penalty for each copy (say -1 per copy for Simple or Average gadgets, -3 for Complex, and -5 for Amazing), (b) apply +1 per copy to the (1d-1)x$100 roll for scrounged cost, or (c) require a search roll to locate a new place to scrounge. If the Scrounging roll fails, and you have to buy the parts, I'd THEN let you both divide costs for parts as the retail cost of the item, divided by 100, x20%. I'd divide time to assemble the prototype by 2.

Does that cover everything?