Make a list of all the steps to make the part, ask the people who will do that job how long it will take, ask payroll how much those people are paid. Ask the supplier how much the rough stock will cost. Ask the inspectors how long they will take to check the part. Add or add, then multiply for each step, and then add it all and that's an initial estimate. If your supervisor tell you other things to include, then include those.

After a while if the company doesn't go broke, you know the estimates are good. If the company did go broke, the estimates weren't good.

I'd go to some machine shop and show them the part, and ask about what it would cost for X amount of parts. And then you have an idea of cost.

some considerations:
1. shape/geometry of the part, more complicated means more cost.
2. type of machining (relate to item 1)
3. material
4. manhour, utilities, rental, etc.

better send your drawing to few machine shops.

R.Efendy