That may be quite reasonable given costs, but it makes that $1000 action that started all the fuss look a lot more appealing. And the $1300 actions from C. Sharps look better and better too.
Not everyone wants a thin side or a round top. Perhaps most do, but not all.
Actions cost a bunch - I don't think your estimates are out of line. But I don't think too many can afford them either. That is in the price range of Joseph Lozito and I wonder if he sells very many Borchardts for which he has many fewer competing producers.
If the revival of the mid-50s varmint rifle takes off, you might have a hell of a corner on a lucrative market. I don't know, but I wish you luck.
Brent