There is a departure fee for Peru, I believe is $25 or $28. Vietnam was about $15 (I paid with their currency so I forgot the exchange rate already), $12 for Thailand...there is an entry fee for Dominican Republic for most countries also.
The departure fee also depend if you are flying domestic or international. There is no departure fee out of Germany (European Union countries), the US, and the Bahamas.
There is a departure fee "airport tax" as it was called from both Zambia and Ecuador. These were both $20 or $25.
The biggest ripoff (departure tax) I ever paid was leaving Venezuela which was I believe 50$US ???? and you have to pay cash before you can join the ticket line,if I had knew I would have got a boat to Trinidad.
The next highest was leaving Columbia, 30$US cash at desk which slightly took the edge of two of the most friendlist places I had been to on my travels but thats life!!!!!!!!!
al de bes
Seeing as you are talking of Buenos Aires (S. America). I paid $20 US leaving Asuncion, Paraguay Feb 05.