Evaluating and controlling the development costs during the unmanned aerial vehicle （UAV） conceptual design phase can improve the cost-effectiveness ratio of UAVs. This study established a multidisciplinary design and optimization （MDO） framework aimed at minimizing UAV development costs. It carried out the design trade-off of UAVs under the constraints of aerodynamic performance and mass properties， obtaining the UAV solutions and cost suggestions that take into account development cost. The optimization framework was based on the OpenMDAO multi-disciplinary analysis and optimization process. It used OpenVSP to establish the geometric and aerodynamic analysis modules for the UAV and employed the partial least squares method to construct the cost estimation model. This enabled the seamless integration of the design strategies from the overall parameter design of the UAV to the multi-disciplinary analysis and the optimization of the development cost. By optimizing the typical low-cost high-performance UAVs， the results show that when the lift-to-drag ratio is reduced by 6.53%， the maximum take-off mass decreases by 8.17%， and the development costs are reduced by 4.01%. The results demonstrate that during the conceptual design stage， through the optimization of the overall parameters of the UAV， it is possible to meet the aerodynamic and weight constraints while ensuring low development costs. The feasibility of the constructed MDO framework based on development costs has been verified， and it has provided effective suggestions for the design of a UAV with low development costs.