DJI Official Store via Newegg offers the refurbished DJI Phantom 3 Professional 4K Quadcopter with 4K Camera for $539 with free shipping. That's tied with our mention from June as the lowest price we've seen. (It's also $402 under the best deal we could find for a new unit.) This quadcopter features a flight time of 23 minutes per charge, 4K video recording, 12-megapixel camera, and 3-axis gimbal. Deal ends September 9.Note: No warranty info is provided.