Bariatric surgery is to date the most effective treatment for morbid obesity and it has been proven to reduce obesity-related comorbidities and total mortality. As any medical treatment, bariatric surgery is costly and doubts about its affordability have been raised. On the other hand, bariatric surgery may reduce the direct and indirect costs of obesity and related comorbidities. The appreciation of the final balance between financial investments and savings is critical from a health economic perspective. In this paper, we try to provide a brief updated review of the most recent studies on the cost-efficacy of bariatric surgery, with particular emphasis on budget analysis. A brief overview of the economic costs of obesity will also be provided. The epidemic of obesity may cause a significant reduction in life expectancy and overwhelming direct and indirect costs for citizens and societies. Cost-efficacy analyses included in this review consistently demonstrated that the additional years of lives gained through bariatric surgery may be obtained at a reasonable and affordable cost. In groups of patients with very high obesity-related health costs, like patients with type 2 diabetes, the use of bariatric surgery required an initial economic investment, but may save money in a relatively short period of time.