I think it depends a lot on how you travel. If you are mainly out for weekends or long weekends, then a good cooler seems like a lighter, cheaper more practical option. You load it and add some frozen water bottles before you leave home, and don't have to think about it again.
On the other hand, if most of your trips are 5 days or longer, a fridge makes sense - again you load it and add ice and it is good for the trip. With a cooler on a trip longer that a couple of days you have to find ice every few days, drain the cooler, and make sure your food doesn't become water logged, none of which you have to worry about with a fridge. Out west anyway it is pretty easy to spend 5 days or more trundling around our public lands without running into a store or gas station (which is a good thing!).
For me anyway, there is a bit of a philosophical note to these discussions about fridges, heaters, water systems etc. The reason we have this big, unwieldy and expensive camper is so to improve our creature comforts and camping efficiency, so we can comfortably spend more time exploring and less time on camp chores and setting up and breaking 'camp' and having to make pit stops. As you start removing the convenience of a fridge, heat, running water, then I quickly see the benefit side of the cost-benefit equation be whittled away.