Do not lower amount of Construction Parts as final product

Look at recipe of "Construction Parts II" it costs 12 "Construction Parts 1" but became 6 at finish.
So change "Construction Parts II" to :
12 X Construction Parts
12 X Electronics
= 12 X Construction Parts II
NOT 6 X Construction Parts II
Is it consumable during production?:D

I think this is a design choice. If this was the case, then costs in terms of number of construction parts would need to be increased for higher tier buildings to compensate, leading to a situation where a silly amount of trucks would be needed to transport all the construction materials needed.