Sao Paolo isn't a cruise port, but is served by the port of Santos. Together, the port of Santos acts as the point of embarkation for about forty cruises every year from MSC, Costa, and Cunard to South America, along with other places.
On average cruises from Sao Paolo are moderately expensive compared to other ports. Cruises scheduled from Sao Paolo during the the peak season of winter are significantly more expensive than the the low season of spring. Check out the diagram below for the average cost per day by month (Cruises only depart from Sao Paolo between January and April).