As a secondary aim, can I propose to measure treatment costs but not compare them? Or should I refrain from this area entirely, except for patient costs?

Studies that directly measure the costs of care will not be accepted. We are, however, interested in applicants providing information in their study that will help facilitate the uptake of successful interventions. Thus, we encourage studies that address cost-related issues, such as the resources needed to replicate or disseminate a successful intervention (e.g., full-time equivalent staff, equipment).