The really big time benefit to flying private is about schedule flexibility rather than security etc (though that's important too). Flying private an executive can turn up and leave 5 minutes later, and be on the road 5 minutes after landing. If a meeting overruns and there's only one commercial flight a day with the relevant city pair, then they're just out of luck. Flying private, it's not a problem.

The economics of whether to own vs rent (netjets etc) is essentially about scale.