Not sure what you mean by graduate tax calc? Where is 19 billion coming from?
These are the numbers as it stands NOW. How many will go to varsity if it was free? 3 or 4 times as students would want to go an study if it was free. Whatever number you reach will skyrocket in a very short space of time.
As mentioned previously, the budget is under severe strain. We have zero wiggle room, and are sitting at record levels of debt and running a large twin deficit.
You are also forgetting that the glorious ANC is also planning a completely unnafordable National Health Insurance which is projected to be R250 - R350 billion over 10 years.
http://www.iol.co.za/business/news/nhi-costs-to-skyrocket-2040660
This is also excluding the nuclear deal that many are against but it seems like it will be bulldozed through and add another trillion rand or so over 20 years.
We as a country cannot afford free tertiary education. Our tax base is too small and we have too many unemployed. We want everything for free in this country, but we cannot afford it.