this question is about a project in Germany, so cost estimates might work differently here. We are having difficulties retrieving the material costs from the subcontractors.

The way we understand it, the threshhold of 20% applies solely to material costs i.e. labour costs are excluded, right? But the way cost estimates work over here is that there is only a total sum per trade. There is no split between labor and material costs so the only way to determine the total material costs is retrieving it from every subcontractor individually and then summing them up. This however leads to the second problem: Subcontractors won't reveal their material costs as it is part of their pricing strategies.

Is there something we're missing? How do we determine the total costs as well as the ones per material? Is there a table or a standard that provides reference costs, so that we would know certain materials amount to x% of total building material costs (for example concrete, reinforcement steel and carpet)?

Thanks in advance!