The flow is not so much of an issue and it is all low pressure to the back pack. They don't use valves to control the flow they have a fly by wire system the controls the throttle on the motor. You can buy a sea-doo jetski for $15000 US that have a 255-hp rotax engine with electronic throttle control.
Now the Jetlev-flyer cost
155 HP = € 99,000 (US $127710)
215 HP = € 119,000 (US $153510)
300 HP = € 129,000 (US $166410)