Hi AB,
SAM's default costs are just a starting point for your analysis. You should do your own research to determine what cost inputs are appropriate for your work. SAM does not automatically change the costs when you change components. For information about the default costs for CSP models in SAM, see
sam.nrel.gov/concentrating-solar-power/csp-cost-data.html.
You should include the cost for all necessary equipment for your design. The default costs are appropriate for the default system design, but if you change the design, you'll also need to change the costs as needed.
The site improvement cost depends on the terrain, and equipment and labor costs for preparing the terrain for the installation.
Best regards,
Paul.