Hi,
The duty cycle on an absorption fridge is 2:3 so it will "burn" 5 kwh per day.
Typically electric rates are 12 cents per kwh, so cost is $0.60 per day or $18.00 per month.
In addition, during winter time it is possible for the fridge to "freeze up". If it does it may self destruct. Norcold makes a kit for preventing freeze ups. It would cost a similar amount per day to run it.