I agree with most posts here-
Electricity > Salt Mix > Food > 2 Part > RODI resin. In that order.
Electricity is the highest, definitely a hidden cost if you have a medium-large tank with a lot of gadgets (i.e. t5, pumps, UV, mix station, AWC).
Another hidden cost if you live in CA? Water. My water bill from salt mix and evaporation is a real cost.