dbrando-
What will this material be used for?
You said ease of machining is a concern, as is raw material cost. But the total cost of raw material, processing, machining, etc is what matters. For example, you might be better off starting with a forged blank of a more expensive material that reduces machining costs, but also provides better mechanical properties. EdStainless' suggestion of Nitronic 40 is good, but Nitronic 40 is only available in a limited size of bar stocks.
A better description of your application would be very helpful.