shipping a manifold

No way in hell at that cost.
You are severely undercutting what it's going to cost in sending out a cast iron manifold.
Depending on distance, and total weight of the package.
I know, as i regularly send out brake and suspension parts, USPS, and FEDEX, and it ain't cheap anymore, in this modern day and age.
Been a while since I have sent out a cast intake. Sorry.