In June he told the commission that Lonmin had "fallen behind" Impala Platinum in the wages paid to rock drillers in the months leading up to a violent confrontation at Marikana in 2012.
In June 2012, about 300 miners approached Da Costa, who was manager of Lonmin's Karee mine, and their representatives told him they wanted a basic salary of R12 500 for Karee’s rock drill operators.
“I pointed out that the increase was extremely high and unaffordable. They thought it was the number that would reward them for the work they do. They said it was a good number,” Da Costa said at the time.
Police witness, Mr X, fell ill on Tuesday and was taken to a doctor, who booked him off for the rest of the day and for Wednesday.
Mr X, who cannot be identified to protect his identity, had been testifying via video link from an undisclosed location. He says he fears for his life and is under police witness protection.
The inquiry is investigating the deaths of 44 people during strike-related violence at Lonmin's mining operations in August 2012.
Thirty-four people, mostly striking Lonmin mineworkers, were shot dead in a clash with police, over 70 were wounded, and another 250 arrested on 16 August 2012.
Police were apparently trying to disarm and disperse them.