The ICM model basically says that your expected dollar prize amount is directly related to your chip stack size as compared to the stack sizes of your competition. It is based on the assumption that all players are of equal ability. This leads to the concept that a chip gained has a lower increase in prize value than the cost of a chip lost.
On the surface, I don’t see why that is counter-intuitive. Sure, the equal capability assumption is questionable and other factors (such as position related to the blinds) are ignored but as a first cut, the model seems reasonable to me.
(If anything, seriously wishing your competition good luck, is much less intuitive
)