One of the major elements when performing a design for manufacturing and assembly methodology is the cost modelling method. A probabilistic cost approach is introduced herein for the series production of a composite wing structure. The proposed methodology should be able to capture changes in the design, the materials and the fabrication processes. Critically, the assembly strategy of the product should also be included to enable realistic multi-disciplinary trade-off studies among several potential build philosophies of the wing structure at the early phase of the design. Furthermore, uncertainty related to the various input parameters, i.e. production, process and cost parameters due to incomplete knowledge, can be considered. Thus, the main effort of the present work is to set up the framework of this methodology, to develop the appropriate cost approach in order to capture manufacturing and assembly costs and further to establish a sensitivity analysis module in order to clarify the dominant cost-drivers of the product. To deal with the uncertainty, Monte Carlo simulation is implemented while Spearman’s correlation coefficients are evaluated and used to perform the sensitivity study. The efficacy of the suggested methodology is demonstrated by comparing a traditional wing design against new more integrated manufacturing techniques, e.g. the co-curing process, for a simplified wing configuration.