Dear readers, I have moved to Substack and I will be writing here from now on: 👉 andrewchen.substack.com In the meantime, I will leave andrewchen.com up for posterity. Enjoy! [Andrew: Paid marketing remains an integral part of many products’ acquisition channels, and one of the key metrics is Cost of Customer Acquisition, which is a nuanced calculation with lots of gotchas. My good friend Brian B