Soft-capped production costs

Want to address the immersion-breaking simplification of unit production costs (like trucks made of iron+copper+rubber). With a perfect understanding of WHY it is done so, I suggest the following:

Let the cost of constructable units diverse more in logical way (like glass, electronics, plastic, aluminum, lubricants etc for t1 trucks), but the required materials missing (or even unavailable for production yet) just add a significant time cost penalty instead, depending on quantity required and material-specific coefficient. Material delivered? Construction time reduced. Not? Bear with month/years construction time.

The idea behind it that you have creative educated pops with free time to produce some things in a garage in their free time to help the colony a little, but it is nothing compared to mass-production scale of a factory.