My mother's Odyssey was loaded with 6 adults and 2 kids in car seats last Thanksgiving going to see Christmas lights. Yes, it's rare, but I've still yet to need to carry a large piece of sheet rock at any time, just not my need. Her mpg isn't as good as the 5, but 23-25 mpg hwy is still respectable with all those passengers. Don't get me wrong, I do like the idea of a pickup, but having an empty bed (trunk) 95% of the time is hardly motivational to purchase one. We used to own an extended cab S10, and fully loaded the bed with luggage and no cover we achieved 29 mpg on a trip to Chicago. This was before kids, but I could purchase a truck and drive it <3000 miles per year and come up alot cheaper than replacing the Mz5 with a full size quad cab.
The side-by-side comparison on fueleconomy.gov between a Ram 1500 with a 4.7l V-8 and the Mz5 shows about a $1000 per year difference in just fuel. Our Mz5 achieves the EPA mpg rating, but your 1500 is getting better than advertised on the hwy so keep up the driving technique.