Ah, history rewrites itself.
I have friends who used to run an Estancia in the north. The idea that there was no need for cheap labor is just silly- On the big estancias, the peones were almost always Gurani. And they seldom got paid much, if any, cash. Mostly got paid in horses and rubber boots and knives, things like that. This was true until quite recently- at least the mid 80s.
And, in the city, there was an enormous amount of cheap labor- it was from Southern Italy, by and large.
Who, exactly, do you think unloaded the ships, built the roads and bridges and buildings and railroads, slaughtered the cows and tanned the hides, worked in the factories, wove the cloth, made the wine, drove the colectivos, and on and on?
Poor italian immigrants, along with other europeans.
And all the abuelos of my friends got paid next to nothing, especially before WW2.
there have always been plenty of poor people in Argentina who work for almost nothing.
Today they are mostly Bolivian, Paraguayan, and, to some degree, Venezuelan.