The importance of automotive cybersecurity is increasing in tandem with the evolution of more complex vehicles, fueled by trends like V2X or over-the-air updates. Regulatory bodies are trying to cope with this problem with the introduction of ISO 21434, which standardizes automotive cybersecurity engineering. One piece of the puzzle for compliant cybersecurity engineering is the creation of a TARA (Threat Analysis and Risk Assessment) for identifying and managing cybersecurity risks. The more time security experts invest in creating a TARA, the more detailed and mature it becomes. Thus, organizations must balance the benefits of a more mature TARA against the costs and resources required to achieve it. However , there is a lack of guidance on determining the appropriate level of effort. In this paper, we propose a data-driven maturity model as a management utility facilitating the decision on the maturity-cost trade-off for creating TARAs. To evaluate the model, we conducted interviews with seven automotive cybersecurity experts from the industry.