Conservation budgets are limited, so it is important to prioritize actions to efficiently protect species. Proxies for cost are frequently used as estimates for inclusion in prioritization problems to make more effective decisions. In this research, we combine real-world cost data for private land and species habitat models into a spatial prioritization problem to explore cost-efficient habitat protection possibilities for species at risk in Ontario. Our findings suggest that protecting species at risk through land purchase may be most cost efficient in areas where species-at-risk richness is relatively high and population density is low, such as in central Ontario. However, the budget required to adequately protect species at risk through land purchase is much larger than is currently available for conservation efforts. Therefore, to effectively protect species at risk in Ontario, we recommend the use of alternative conservation measures, such as easements on private land, to supplement already protected areas.