This was sent to me on 8 June from Buenos Aires and at the time their international letter rate (small, simple) was $29 pesos. A little less than a month after this was sent the rate was increased to $37 pesos. That's expensive. It costs me half that amount to mail a similar letter internationally from Canada. Postal rates in Argentina seem to have gone up a lot lately. I was planning to send some covers to Argentine Antarctic bases this year but when I saw the postal rates I decided against it.
The large stamp shows the Néstor Kirchner Cultural Centre which opened in May of this year. Named after former president Néstor Kirchner, the building used to be an old Post Office before being turned into the largest cultural center in Latin America. The $6 stamp is from the "festivals" series: "Fiesta Nacional de la Noche Más Larga". The day of the longest night being winter solstice in the southern hemisphere. And I believe the last one is a "regular use" issues from 2014... something to do with graduating from University.