I have one new unbuilt still in plastics high end Gryphon Dynamics foldable heavy lift frame for sale. New price 1700USD. Asking 1500USD incl shipping anywhere. This is for true professionals, really impressive rock solid engineering.
https://www.quadrocopter.com/GD-X8-Frame-Kit-1000mm-foldable_p_1057.html
https://www.quadrocopter.com/GD-X8-Frame-Kit-1000mm-foldable_p_1057.html