Imo, the later you enter the less advantage you have since it got 3-2-1 street game. Moreover, you'll have the stack disadvantage, since average stack will be bigger.
there are also the super mega donkey donks and accidental nlmtt player registrations to take into account in the beginning that bust harder than a night w/ your...
You can calculate the value of the chips you are buying with ICM surely? I assume you are getting less than your buyin worth of chips in ICM when you late reg.