1. Introduction
2. Simulation Method and Analysis
2.1. Cluster Properties
2.2. The eROSITA X-ray Background
2.3. Simulation Outline
2.4. Analysis Procedure
3. Results
4. Cosmological Interpretation
5. Discussion
5.1. Dependence of the Relative Uncertainties
5.2. Further Remarks on the Relative Uncertainties
5.3. Occurrence of Catastrophic Failures
5.4. Influence of the Analysis Strategy
5.5. Remarks on the Cosmological Interpretation
5.6. Comparison Between Different Scaling Relations
5.7. Comparison to Other Works
6. Summary and Conclusions