Hmmm, well the energy density of propane is about 30 times that of a lead acid battery, so even if the junk gas refrigerators (which by the way have no moving parts and make no noise) are 5 times less efficient than a 12V DC fridge, they will still run 6 times longer than a 12V fridge for the same volume of power source.
Sunshine and solar would make the difference though.
Hard choices...pay $$$ for a efficient 12V electric fridge that makes noise and may fail in a few years or pay $$ for a propane fridge that makes no noise and probably will fail in a few years also.