$50 million seems like an arbitrary amount of revenue to expect DuoLingo to pull in. How do you come up with that number?

I think it came from dividing the $470M valuation with 10 and rounding up.

Rosetta Stone pull in that much per quarter.

And manage to run at loss, with it.

I guess they might operate at a loss for a few years. While its a difficult goal, but it is possible. They have the biggest market possible. Language is elementary for humans. I think if they can target schools and universities with a commercial model, it could really generate the kind of revenues your talking about.