[math sniped]
We know from above post that it will cost 16 extra dollars for the faster
speed (based on 3.99 gallon fuel)
$16 to save five minutes.

It is worth the extra money if it means landing ahead of the approaching
thunderstorm that's about to hit the airport and getting the plane in
the hangar.

But the fast plane is down 5 minutes sooner.
At $60 /hr fixed costs ...that's $1 /minute
So to get there 5 minutes sooner on a 2 hour (400 mile) flight:
$16 fuel - $5 (tach time) savings = $11
$10 = $2/minute for arriving 5 minutes earlier on the ramp, 400 mile away.
Wow.
I'm seeing a "free lunch" if you choose the slower speed. :-)

But you are soaked or left sitting in the plane on the ramp until the
rain stops.