What drives the prices of arms and ammunition sold at illicit markets? Do the prices of illegal arms soar during episodes of marked insecurity, such as conflict onset? This article seeks to advance knowledge on the dynamics and determinants of weapons prices through the quantitative analysis of illicit arms market price data in Lebanon for the period February 2011 to September 2012. The article also examines the relationship between arms and ammunition prices in Lebanon, and reported conflict fatalities in Syria, as the period under study overlapped with the onset of conflict in the latter country. Key results include strong, statistically-significant correlations between the prices of arms and the prices of ammunition in Lebanon, as well as between the prices of arms and ammunition in Lebanon and reported conflict fatalities in neighbouring Syria. These findings highlight the value of monitoring illicit arms market prices, including prices for a diverse range of weapons and ammunition, to improve our understanding of both illicit markets and conflict dynamics. The strong correlations observed in the article also suggest that crowdsourcing methodologies used by organisations monitoring killings during the Syrian conflict can effectively capture variations in conflict intensity over time.