Whist the initial buy price might put off many people, especially when comparing the prices of them against a simple esky an Ironman 4x4 12v fridge really is one of the best investments you'll ever make!
Ice has a usable. Even using some smart methods like blocks and a good quality esky your ice will be lucky to last a week. A fridge on the other hand. So long as you keep your battery topped up will keep going and going and going. Keeping the battery charged up generally required doing a long drive every few days or running a sufficiently sized solar panel.
Once you account for all the ice that you need to load into an esky to keep the contents cool you'll lose a lot of real estate that in a 12v fridge can be used with more food and drinks!
An eskies ice will melt over time. And often you'll find your food floating in amongst the ice by the end. Should the food not be properly sealed it can often soak up water or worse, make the water fetid. I'm looking at you open, floating packets of bacon! A fridge on the other hand doesn't use melting contents to keep them cool, instead using a compressor which will keep ticking along keeping everything cold and dry!
An esky doesn't have any form of temperature control, Ironman 4x4 fridges on the other hand have a temperature control built in. The compressor works only enough to maintain that set temperature, ensuring consistency across a day when it is hot during the day and cool at night. This ensures the contents of your fridge are maintained at an ideal temperature and maximises their fridge life and ensures your contents are safe to consume!
Stopping off at a servo to grab ice and working out how many bags are needed is no longer a problem. Not only do you get to save on the small ongoing cost of buying ice, but you save the inconvenience of having to go buy it. Just switch on your fridge if it isn't already running, load it up with food and away you go! (best power efficiency gained from pre-chilled fridge via 240v and loading fridge with pre-chilled food & drink).