True, argentian does have a higher GDP per cap than those countries you've listed, which are definitely developing (or in the case of Zimbabwe downwards, underdeveloped)
From
The World Bank
For operational and analytical purposes, the World Bank’s main criterion for classifying economies is gross national income (GNI) per capita. In previous editions of our publications, this term was referred to as gross national product, or GNP. (More about this change in terminology). Based on its GNI per capita, every economy is classified as low income, middle income (subdivided into lower middle and upper middle), or high income. Other analytical groups, based on geographic regions and levels of external debt, are also used.
According to
this, Argentina is a developing nation as is Beliza, Costa Rica, but both Costa Rica and Argentian are high middle income economies.