I care somewhat, and for two reasons besides money. One, better mileage equals better range. Better range means greater flexibility in planning fuel stops. Two, better mileage means less carbon emissions. That's controversial, of course, and one could argue that if I really cared I'd tent camp in a Prius. Not going there, but in a case of other things equal...
It would not be my highest consideration, but I don't consider it irrelevant, either.
As an indication of how far technology has come, my 2014 Chevy Roadtrek on the Express 3500 van with the large 6.0L V8 and newer 6-speed HD transmission yields 17-18 mpg cruising at 65-70 mph (fully loaded, empty tanks, four on board). The 31 gal. tank gives it a working range of 450 miles. Diesels can do better still, but at an even higher cost.
That said, the Chinooks are very attractive and unique. They are really compact C's on an F450 or equivalent cutaway chassis, so it's really not fair to compare the fuel economy to a B-van.