The paper examines the links between degree of intellectual disability, challenging behaviour, service utilisation and cost for a group of people with intellectual disabilities living in care accommodation in England. A cross-sectional survey was conducted of people with intellectual disabilities, identified via provider organisations, with supplementary collection of costs data. Multivariate analyses of cost variations were carried out for 930 adults with intellectual disabilities. There were strong, nonlinear, interdependent links between degree of intellectual disability, behaviour, service use and costs. Higher costs were associated with more severe intellectual disabilities and more challenging behaviour. Sector and scale of residence also influenced cost in quite complex ways. Access to and use of services by people with intellectual disabilities were not always appropriately linked to perceived or actual needs. Policy makers and local commissioning agencies need to explore the sources of cost variation between individuals, sectors and types of accommodation in order to achieve national policy objectives on quality, choice, independence and inclusion.