It is tit-for-tat, as the USA charges Chilean citizens when they enter the USA.
The stamp is good for as long as the passport is valid.
SS Norway (12 times) '85 - '97; Radiance OS 06/01; Island Princess 11/04, Grand Princess 11/04/05, Golden Princess 7/21/06, Golden Princess 2/24/07, Explorer of the Seas 12/23/07, Island Princess 11/15/08
I have just encountered the same for flying to Brazil to catch a Holland America. It is my understanding these fees are being charged because the United Sates charges the same fee for citizens from that country to enter the US. I am told that Brazil is extremly strict and without a visa you will not be able to enter the coutry even for the purpose of boarding a crusie ship. I have yet to get a reply from the US State Dept as to why this has to be that way.