Over the past 15 years the topic of information security economics has grown to become a large and diverse field, influencing security thinking on issues as diverse as bitcoin markets and cybersecurity insurance. An aspect yet to receive much attention in this respect is that of secure software development, or 'SWSec'-another area that has seen a surge of research since 2000. SWSec provides paradigms, practices and procedures that offer some promise to address current security problems, yet those solutions face financial and technical barriers that necessitate a more thorough approach to planning and execution. Meanwhile, information security economics has developed theory and practice to support a particular world-view; however, it has yet to account for the investments, constructs and benefits of SWSec. As the frequency and severity of computer misuse has increased, both areas have struggled to impart a new mindset for addressing the inherent issues that arise in a diverse, connected and functionality-driven landscape. This paper presents a call for the establishment of an economics of secure software development. We present the primary challenges facing practice, citing relevant literature from both communities to illustrate where commonalities lie-and where further work is needed. Those challenges are decomposed into a research agenda, deriving from the application of principles in both themes a lack of models, representation and analysis in practice. A framework emerges that facilitates discussions of security theory and practice. CCS Concepts •Security and privacy → Economics of security and privacy; Software security engineering; •Software and its engineering → Software design tradeoffs;