Did the math and strictly on a fuel usage basis it looks close between a Beechcraft Bonanza with four or six people and a 737 with 125 people. We have to convert to true airspeed and use a standard travel distance to compensate for the radically different speeds
Beechcraft Bonanza:
basic numbers from the intertube: 169 knots @ ~15kft, 16 gal/hr
true airspeed: 211 knot (
http://www.hochwarth.com/misc/AviationCalculator.html)
assume 100 nautical mile test run.
time = distance/speed: 100nm / 211knot = 0.47hr
fuel burn: 0.47hr*16gal/hr: 7.52 gal
fuel per person (6 people): 7.52 gal / 6 people = 1.25 gal-per person
fuel per person (4 people): 7.52 gal / 4 people = 1.88 gal-per person
Generic 737:
basic numbers from the intert-tube: 0.74 mach at 30kft, 5500 lb/hr-> 816 gal/hr
true airspeed: 436 knot
assume 100 nautical mile test run.
time = distance/speed: 100nm / 436knots = 0.23hr
fuel burn: 0.23hr*816gal/hr: 187 gal
fuel per person: 187 gal / 125 people = 1.4 gal-per person
There are 1001 assumptions in this but it looks like the two are close in terms of fuel usage and it could go either way with the exact number of people on board.
EDIT: But they would be using different types of gas that cost differently and Delta does not buy at Joes-gas-n-fly, but Delta may have less choice where they buy and local taxes...