Odds of getting any manufacturer's cost is slim. You also have to take into account that cost varies greatly depending on complexity/geometry of the casing, casing material, quantity ordered, and of course variations in price from manufacturer to manufacturer. If you want a true measure of manufacturing cost, I would suggest you get a 3D CAD model of your desired design and send it to a manufacturing firm with your desired material and quantities. Most companies will be able to quote you a price per unit or batch and a lead time.