Risks are significant when implementing large-scale projects such as 5G. The higher the overall risk of the 5G project, the lower the operators’ willingness to invest in millimetre wave spectrum and vice-versa; i.e. the price of the spectrum should be negatively correlated with the overall project risk. In this paper, we propose an array-based method for estimating financial risks when introducing 5G and its correspondence with spectrum prices. The method is based on Monte Carlo simulations, for deriving an appropriate maximum value for the operator’ willingness to pay for a 5G license.