Hi, this is Andy here, the Founder/CEO of Proton. As former scientists, we don't do what we're doing to make the most money (otherwise we wouldn't have picked science as a profession). There's no price which we would sell Proton to Google or Facebook. We also don't need to because thanks to the strong support of the community, Proton has the resources to thrive and grow as an independent organization. Safeguarding this independence is how we ensure that over the long term, we can always put user interest above all else.

-Protonmail Founder, 2 years ago, for what it's worth.