Objective Financial costs are a significant barrier to the uptake of empirically supported psychological interventions in clinical settings. Training may be among the largest of these costs; however, the potential magnitude of these costs is unclear. The aim of the present study was to develop a hypothetical model of potential training costs associated with adopting a novel therapy using systematic review of anticipated training durations and publicly available data on workshop costs, training materials and income. Methods Direct and indirect costs were estimated for reference categories being cognitive behavioural therapy for social anxiety disorder delivered by registered psychologists. These were based on averages of 39 workshops and eight treatment manuals available in Australia identified through online searches. Results This model demonstrated that upper cost ranges for training can exceed A$55000, and even didactic training (reading manuals, attending workshops) may cost up to A$9000. Indirect costs of forfeited income account for a substantial proportion of these costs. Conclusions This hypothetical model highlights why training costs should be considered in decisions about disseminating and implementing novel empirically supported psychological interventions, particularly within private workforces. In addition, the direct return on training investment for practitioners in private practice is unclear, and may vary based on caseloads and current treatment modalities. Initiatives to track competence, support training and identify novel training solutions may be required to ensure the sustainability of high-quality mental healthcare. What is known about the topic? Financial costs are one of the leading factors determining whether empirically supported mental health treatments are adopted or sustained. Training costs may be one of the largest costs of disseminating and implementing novel psychological therapies within existing workforces, including both direct (e.g. workshop fees) and indirect (e.g. lost income) costs. However, little is understood about the potential magnitude of these costs. What does this paper add? This paper presents a hypothetical modelling of potential costs associated with adopting a novel therapy, with reference categories for an empirically supported treatment (cognitive behaviour therapy) for one mental disorder (social anxiety disorder) for one mental health profession (psychologist). This model was developed and populated using systematic review of anticipated training durations and publicly available data on workshop costs, training materials and income. What are the implications for practitioners? With potential costs for adopting one novel psychological intervention exceeding A$55000, we highlight why training costs and pathways should be a focal point for ensuring the sustainable provision of high-quality mental healthcare in Australia.