Systems and methods are disclosed for generating cost estimates. In one implementation, a cost estimation system includes cost object metadata describing a mapping between functions at a cost estimation system and corresponding functions at a cost evaluation system. Based on the metadata, the cost estimation system determines whether a cost object requires evaluation in the cost evaluation system and, based on that determination, provides an evaluation request for the cost object to the cost evaluation system. In response to the evaluation request, the cost estimation system receives cost data determined by the cost evaluation system and calculates the cost estimate.