Aidan’s response to Vasco’s comment you quoted is a starting point:
I would actually expect our marginal multiplier to be much closer to our average multiplier than the CEARCH method implies. Most importantly, I expect most of our marginal resources are dedicated to identifying and executing on scalable pledge growth strategies. I think this work, in expectation, provides a pretty strong multiplier. By comparison our average multiplier includes some major fixed costs (e.g., related to running our donation platform).
Aidan’s response to Vasco’s comment you quoted is a starting point: