The confrontation of the macro- and micro-economic approaches of hospital costs is a recurrent question, in particular for pathologies where length of stay is highly variable, like acute myeloid leukemias (AML). This monocentric and retrospective study compares direct hospital medical costs of induction and relapse treatment sequences for AML, valued according to four different approaches: the analytic accounting system of our hospital, the French Diagnosis Related Group (DRG) cost databases of hospital discharges (readjusted, or not, to actual hospital stay duration), and official tariffs from the new French DRG prospective payment system. The average cost of hospital AML care valued by the analytic accounting system of our hospital is 61,248 euros for the induction phase and 91,702 euros for the relapse phase. All other national valuation methods result in a two- to four-fold underestimation of these costs. Even though AMLs are now individualized in the 10th version of the French diagnosis related group (DRG) classification, the impact of this issue in other pathologies is going to increase with the gradual implementation of the French DRG prospective payment system. That is why it must be assessed before the progressive extension of this financing system.