The introduction of shared autonomous electric vehicles (SAEVs) brings along many advantages. Most of these advantages can be achieved when SAEVs are offered as on demand services by fleet operators. However, autonomous mobility on demand (AMoD) will only be established if fleet operation is economically worthwhile. This paper proposes a macroscopic approach to modeling two implementation scenarios of an AMoD fleet, differ- ing in the number of deployed SAEVs. The city of Zurich is used as a case study, with the results and findings being generalizable to other similar European and North American cities. The simulation builds on the traffic model of the canton of Zurich ( Gesamtverkehrsmodell des Kantons Zürich (GVM-ZH)). Financial profitability is based on the simulation results which are combined with a comprehensive SAEV cost analysis. The results demonstrate that, depending on the scenario, journeys can be offered profitably to customers for CHF 0.66 or CHF 0.56 per kilometer. While larger fleets allow for lower price levels and increased profits in the long term, smaller fleets exhibit elevated efficiency levels and profit opportunities per day. The paper concludes with recommendations on how fleet operators can prepare themselves to maximize profit in the autonomous future.