This is the final part of the series of articles devoted to the development of a decision support system for choosing the optimal post-quantum key encapsulation mechanism. Efficiency of the methodology proposed for choosing the optimal implementation of the post-quantum cryptographic algorithm is evaluated and substantiated. The economic feasibility of approach is shown and its positive impact on the quality of the cryptographic information protection subsystem is demonstrated. Efficiency comparison of the prototype of the decision support system with existing software products aimed at supporting decision-making in the field of information security is carried out. The consistency of prototype’s recommendations with the conclusions of analytical studies in the field of post-quantum cryptography is checked.