Accounting literature provides many examples of how it has helped healthcare decision making. There is no evidence of how healthcare has helped accounting. This is a unique study which views accounting decision making from a non-business perspective of healthcare decision making, through treatment cost interactions. Relationships between illness and illness related costs are viewed from a treatment perspective showing that cost interactions are more complex than would be suggested by current accounting decision making models. The result is that managerial decision making needs to provide flexibility to allow unique cost interactions which are expected but not quantifiable to be included in decision metrics. Both financial and non-financial information is shown to be of continued importance in decision making, but suggesting that some healthcare costs may mask themselves as irrelevant even though they are not.