Radiotherapy costs are an often underestimated component of the economic assessment of new radiotherapy treatments and technologies. That the radiotherapy budget only consumes a finite part of the total cancer and healthcare budget does not relieve us from our responsibility to balance the extra costs to the additional benefits of new, more advanced, but typically also more expensive treatments we want to deliver. Yet, in contrast to what is the case for oncology drugs, literature evidence remains limited, as well for economic evaluations comparing new radiotherapy interventions as for cost calculation studies. Even more cumbersome, the available costing studies in the field of radiotherapy fail to accurately capture the real costs of our treatments due to the large variation in cost inputs, in scope of the analysis, in costing methodology. And this is not trivial. Accurate resource cost accounting lays the basis for the further steps in health technology assessment leading to radiotherapy investments and reimbursement, at the local, the national and the worldwide level. In the current paper we review some evidence from the existing costing literature and discuss how such data can be used to support reimbursement setting and investment cases for new radiotherapy equipment and infrastructure.