Automatic Milking Systems (AMS) are expected to reduce dairy working hours, however, they may increase production costs and reduce dairy incomes. In this paper revealed preference theory is used to confirm a farmer’s decision whether or not to install an AMS. Data provided by a dairy farmer who is milking only by AMSs is used. The reduction of dairy income could be recovered utilizing the information provided by the AMS to improve dairy feeding and herd management. It may be possible to introduce AMS to not only farmers with a strict preference for reducing work hours, but also to farmers with a strict preference for increasing or maintaining dairy income.