A factory decides to stop making cars and start making motorcycles instead. When it made cars, per month, it cost $100 for materials, they could make 4 cars, and they sold each car for $50. Now that they make motorcycles it costs $250 for materials, but they sell 8 of them for $50 each. How much more profit do they make per month selling motorcycles instead of cars?
Please reason step by step, and put your final answer within \boxed{}.
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