Oh, I don't doubt that they have a very sophisticated model for this. I'm just saying they probably take customer acquisition cost into account in the model too

Oh, I don't doubt that they have a very sophisticated model for this. I'm just saying they probably take customer acquisition cost into account in the model too. "I bet they do it for free marketing" doesn't mean "I bet they didn't do the math". It means "I bet their marketing department measures everything and is good at math too."