A private jet saves time on the ground, not in the air. The cruise speed of a business jet and an airliner is similar, and on some routes the airliner is faster. The time you save comes from how the journey is built.
Take a trip from Delhi to a district town with no direct flight. By airline: drive to the airport, arrive two hours early, fly to a hub, wait, take a second flight to the nearest airport, then drive three hours by road. That is a full day, and often a night in a hotel.
By charter: a shorter drive to a general aviation terminal (for private flights), a short wait, one flight to a nearer airfield, and a much shorter drive. The flying time may be similar. The day is not.
On a busy route the answer flips. Delhi to Mumbai has many daily flights. A commercial ticket, especially for one person, is much cheaper. The time saved is an hour or two, not a day.
The cost comparison depends on how many people travel. Charter is priced per aircraft, not per seat. Six premium tickets, six airport transfers and a hotel night caused by a bad connection add up to far more than one economy fare. Compare the full cost of the airline journey, including the working days it uses up.
Time is not the only reason. On a charter, you can talk freely in a private cabin. You can move the departure time when a meeting runs late. And you can reach airports that airlines do not serve. Whether that is worth the extra cost depends on the trip.
The simple rule: for one person on a busy route, fly commercial. For a group going somewhere hard to reach, or a day that cannot work any other way, charter often wins once you count the full cost, not just the fare.