Join Date: May 2014
Posts: 7,826
^ This.
If they are paying 5 spots and there are 70 left then ICM really isn't a factor this far away from the money. Just get as many chips as you can.
If you need to know a dollar value then the approach you use is fine this far out.
What ICM in satellites is about is that if you have 0% of the chips you average 0% of the seats, but if you have 50% of the chips you don't average 50% of the seats because you can still only win one seat - so chips are not of linear value (in other words every new chip is worth progressively less).
In your case, you (and almost certainly everyone else in the satellite) have so few chips relative to the amount you need that doubling your stack does (almost) double your chance of getting a seat.