After reviewing the Reddit Post again I think that the Pledge Factor is not as important as I thought it might be.
Link: https://www.reddit.com/r/cardano/comments/hnm3l6/shelley_incentive_parameters_what_you_need_to/
Based on this a Pledge of 1M is providing a 0.04% better ROS (being 3% higher) compared to a zero Pledged Pool.
Means: A pool with 0 Pledge and 1% margin is equal with a Pool with 1M Pledge and 4% Margin
The much bigger impact is the Pool Saturation, because in a low Saturated Pool the Operator Cost is eating a higher portion than in a high Saturated pool where the Operator Cost is splitted to many delegators. Good rates are achieved with over 10M active stake. Still 10M has a 11% higher rate compared to a 3M active stake pool (5,46 vs 4,89).
As a final conclusion my best guess for the expected return is shown below.
Note: I updated the expected Rewards per Block to 1100 ADA to end up with realistic ROA Numbers.
