Our ballpark for that is if everything goes smoothly we lose 90 minutes. Any problems boost that to two+ hours. “Problems” usually involving law enforcement, other antsy passengers, or if the airplane picked that time to break down. Or us dropping into an airport at a time our ground team didn’t have enough spare people or facilities to take us expeditiously.
We can get it down to an hour for semi-preplanned stops. Which are things not built into the schedule but which become known on the day of, but before takeoff from the first station. That scenario plays out about like this:
Years ago I used to fly a flight that was out near the edge of the range of that model airplane. From the typical average daily situation, having a bunch of extra cargo, extra unfavorable winds, extra high temperatures at the departure station, or extra widespread crappy weather at the destination could trigger a need to stop for fuel along the way. Any given flight could tolerate 2 hard strikes against it, or maybe 3-1/2 easy ones, but not 3 hard ones or even a smidgen of all 4. That much aggregate bad luck all at once would force a stop.
On those flights where the stop was needed it’d be obvious a couple hours before departure. So the designated fuel stop airport could be alerted several hours in advance to have a gate and ground crew ready at the expected time. And we could reduce the fuel load for the first departure to be only enough to make it to the planned stop station. Which lets us fly higher and faster. We could also plan both legs at faster than normal speeds. We’d also pick the fuel stop airport to be a small one with light traffic, say dropping in to Des Moines rather than nearby O’Hare.
So we’d come whistling in at speed, land, shut down at the gate, the fueler would be right there, they’d pump us full in 20-ish minutes while we got fresh paperwork for the next leg and prepped the jet to go again.
If everything hit perfectly we’d be 25 minutes at the gate, 40 minutes on the ground, and lose about 20 more minutes due to slower speeds in the climb and descent vs cruise as well as the maneuvering for takeoff & landing.
Done like that it “costs” about 60 minutes versus the non-stop.
HQ tells us that ballpark it costs $50K to divert a 737/A320 size airplane to deal with a passenger problem or a weather problem. Figure $200K for a 787/777/A330/A350.