The iPhone app example in the presentation confuses me.

The way it is presented, it looks like the conclusion is that you should always be willing to spend an additional $6999.99 no matter how much you have already spent. If current you is willing to spend the extra money regardless of whether you have already spent $4000 or $10999.99, then I don't see why future you would feel any different.

I would think that you should take in to account the fact that your original estimate of the cost was too low. Given that this is the case, you should expect that your current estimate of the cost to finish is also too low. I would multiply your cost to finish estimate by (current estimated total cost) / (original estimate) and only continue if that result is less than $7000.

Going over this in the presentation would introduce complications to the problem that would most likely lead to even more confusion, but when the details are left out, it looks like you are endorsing the same decisions that the sunk cost fallacy would lead to. I suggest changing the example to something else entirely.