I don´t know what technique is used to manufacture metallic parts having such an intricate geometry to be honest, but the approach that seems more feasible is not to cut a solid piece, but rather to split the original draw into many sheets ( such as sections of a tomography ) and assemble all them stacked, turning a little each plate at the appropriate angle.
In order to provide an anti-aliasing of the inner surface, could finish in nickel or another material suited for this application.