The manuscript focuses on the situation before the execution of construction activities starting and after the crystallization of the contractual object between Public Authority and contractor. The aim of the article is to investigate the interpretation of mathematical model of measurement of a public work cost after contractor’s selection and before the start of contractual activities. Our study results have been drawn through the interpretation of equations, which have been extracted by the study of the multiparameter polynomial, as these have been developed and proven in the study “Measurement of the Cost of a Public Works Project: The Case of Greece”. Taking advantage of the mathematical model, which was defined in the previous study, we develop the comprehension of critical conditions, which determine finally the equivalent in money of cost of each technical commodity for the purchaser and shape the execution conditions of competition in the construction market. Due to the relation of Hellenic legislation with that of EU, the suggested mathematical cost measurement model of a public work and the conclusions of the present article can be used in further study related to a critical evaluation between Earned Value Management Method and Earned Schedule Method. Despite the Hellenic experience, the approach of cognitive object and the conclusions which are reached could be applied in the international practice, if we take into consideration that the process of contractor’s selection that is used at least in the European Union, is similar.