I joined Proton just a few days ago, and I’m paying for it so I can use my custom domain.

I watched this interview and it raises a huge question for me (link includes timestamp): https://tilvids.com/w/q1mZzv6eq3iULLmGdV6w6M?start=6m20s

In this interview, Andy Yen says about gmail et al “there’s no such thing as a free lunch”. Then, in nearly the same breath, he boasts that most Proton users don’t pay, they use the basic service for free because that’s all they need.

So my question is: if there’s no such thing as a free lunch (which there isn’t), how come Proton can offer it?