Sometimes, economies of scale don't just come automatically with scale. You actually have to make economies of scale happen when you invent new processes - this often means creating new machines or new methods that can be done by untrained people.

The process for creating these fake meats is complicated and long, so there are certainly a few novel steps in there. I'm guessing that a few key steps do not scale well today and have significant technological barriers to scaling. I have no idea what they could possibly be.