<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by ExMo:
you only need to pay it once for the remaining life of your passport </font>
I flew to SCL two weeks ago and asked about the fee being for the "life of your passport", and was told that as I held an Australian passport the "stamp" was only valid for 90 days.
So it looks like paying $100 as US citizen ends up cheaper in the long run.
Dani