Let us first start with what economics is not. Economics is not entirely the study of efficiency. It is also firstly, and primarily, the study of welfare of society.
Economics is not the study of money. That is accounting. Accountants are bean counters (and I'm gonna be one).
Economics is often split into two fields, microeconomics, and macroeconomics. Microeconomics try to deal with individual choices, and how these interact to affect variables like price. Macroeconomics deals with aggregates like GDP and aggregate demand.
Economics is only superficially the study of scarcity. It concerns itself about questions like government intervention, unemployment, inflation, levels of trade, and distribution of income. Through the study of economics we try to obtain the best possible choices for governments and individuals to make, to better our lives.
Economics was seen as the dismal science because of Rev. Malthus's predictions in the 19th century. His oft misquoted theory says that since population grows at a geometric rate (exponentially) and the means of production of food has grown at an arithmetic rate (linearly), there will be a time of great suffering in the future. The only way he saw through this problem was what he called "moral restraint" (stop buggering each other you rabbits), or "vice" (go to the brothel, where REAL contraception is used). He didn't forsee the changes in patterns of population growth, or that technological advances would also increase production exponentially.
Economics long moved beyond utilitarian views. Melancholia's statements are rather unsupported, and only seem to seek to slag off economics. Ever heard of the Rowlesian Welfare function, O ye of narrow views?