They express ecological limits which should not be exceeded in any case. If thresholds exist, the problem becomes more transparent when they are expressed in physical terms. If no thresholds exists, a social decision has to be made on the basis of peoples preferences. Within this discussion and decision making process, again, results from monetary valuation studies can be helpful, independent of the magnitude of their results. The study really switches between paradigms.
Monetary valuation is an accounting methodolody for estimating relative prices.
When values become infinite, the microeconomic approach of welfare theory goes beyond its limits. While money only tells us stories about relative scarcity, infinite monetary values mean absolute scarcity. Figure a shows normal supply and demand curves as they are used in the study, i.e. the study is based on a neoclassical weak sustainability approach dealing with questions of allocation. However, figure b only illustrates theoretically assumed functions which have not been applied in the study. Social costs and sustainability.