Illicit firearm markets constitute a significant component of global illicit economies and assume a central role in facilitating violent and organised criminal activities. Despite restrictive legislation across many jurisdictions that aim to limit access to firearms, criminal actors continue to access firearms through a range of channels, particularly via criminal networks and informal social connections. However, little is currently known about the factors that influence the prices of firearms in these illicit contexts. Building on the existing literature and drawing on interviews with 75 prisoners incarcerated across sixteen correctional centres in two Australian states—South Australia and New South Wales - this paper examines the factors that influence the prices of illicit firearms. In doing so, this paper contributes new empirical insights into how illicit firearms prices are structured and negotiated, as well as the social and market forces that influence illicit firearm pricing. Overall, our findings suggest that illicit firearm prices are affected by a combination of restrictive policy environments, supply and demand dynamics, perceived risks of buying and selling illicit firearms, the unique characteristics of specific firearms, and social dynamics including closed social networks and interpersonal trust. We conclude by reflecting on the implications of our findings on policy and practice.