I would say that depends on whether your wheeling is such that are placing yourself at serious risk from getting lost or not. A fridge is a convenience, one can survive on trail mix for a long time without one. Getting lost 50 miles out in the desert is not so great. Now, even with a GPS, though, you still need to have maps, compass and know where you are so if the GPS conks out you don't automatically get lost, IMHO. So one could argue it is also a convenience in a sense. But I think it's more than that, the GPS is a terrific tool that I would not go out without any more, and providing it's actually working a GPS makes it basically impossible to get lost, not so with a map.
But also to get to your basic point, a $150 GPS will do just fine. Not too many $150 new fridges out there, though.