Most of the cost for these things is safety and developing mass-production. The flight and stability development alone is probably a good quarter of the cost. Furze's bike was two gas motors with chunky propeller blades with direct handlebar controls, no smarts in it at all. I'm not denigrating Furze's bike at all, it's a ridiculous technical feat. But it's always going to be more expensive to bring something to market for the lowest common denominator versus building personal once-offs.