I doubt manufacturing gets a percentage cut - doubt they want such a cut. Manufacturing likely charges by how much you ask them to produce. They will quote you a price for your order and maybe include a discount for large volumes.

Manufacturers gets paid, and they'll expect to make a profit. No, they don't take a percentage, but that's a rather academic distinction when the unit cost for manufacturing is $5 and your product isn't marketable with a price exceeding $50.