This is a discussion on Should you always buy the “Add on” in Tourneys? within the online poker forums, in the Tournament Poker section; In most rebuy tournaments, at the end of the rebuy period you are allowed to Add on to your chip stack by paying the tournament
On 888 poker the add-on is twice the original chip stack. So for the add-on to not be profitable, the ICM value of additional chips have to be less than half the ICM value of the other chips in the tournament. Its pretty difficult to imagine any realistic scenario, where that is the case. Usually even the chip leader is not that far ahead.
I personally try to avoid these type of tournaments but its getting harder and harder to avoid. The only time I dont do the add on is if I am so sort that the add on does not make my stack big enough to the blind level.