The energy prices and external costs do not impact the costs of the dam project in spite considering the costs to low price level as suggested in above analysis (Ampbell and Brown, 2003). The cost of the dam project is still lower than the cost of desalination project. The operating component is made at 50% of the actual cost still the real price of the water $ per ML is US $8221.22 for 50%, US$8534.45 for 100%, US $8847.68 for 150%, but on the same side, real cost of the water $ per ML is US $7335.13 for 50%, US $7335.3 for 100% and US $7335.13 for 150% increase in energy price. This indicates that in spite of increase in costs there is not much increase in real price for water $ per ML. The costs of $ per ML is still higher for Desalination project. The value of the external costs is considered highly volatile that suggests that these parameters are uncertain to the project cost over time. This means increase in price further will result to increase in the desalination project. The variation of the ±100% is possible in the prices of the external factors in spite of that at zero level of prices, for the external factors the costs of the dam project still higher (Australian Bureau of Statistics, 2008). The material and labour also impacts the costs of the projects, but still at 50% reduction in all costs, the cost of the dam project is lower than the desalination project in all the scenarios in 50% sentiment analysis.