They were also sceptical the commitments were of sufficient scale to meaningfully change the bleak economic outlook.
Ramaphosa is trying to revive Africa's most industrialised economy after a decade of stagnation. He has promised sweeping reforms, but progress has been slow due to opposition from labour unions and parts of his African National Congress party.
"It is pleasing to see that investors still consider South Africa as a country that has much to offer," Ramaphosa said.
At a summit last year, Ramaphosa set a goal of attracting $100 billion of new investments over five years and quickly secured more than half that amount in pledges.
But many of those promises are yet to translate into projects that could lower the 29% unemployment rate or lift the growth rate above last year's level of 0.8%.
On Wednesday domestic firms like telecoms company MTN and paper company Sappi made some of the largest pledges, of 50 billion rand and 14 billion rand respectively. Others were made by carmakers, textiles firms and insurer Discovery.
State-owned freight firm Transnet promised 23 billion rand and the airports management company 12.8 billion rand. Few overseas firms made pledges.
Of those that did, like Chinese electronics manufacturer Hisense, relatively small amounts were promised.
Kevin Lings, chief economist at asset manager Stanlib, said the government's focus on deregulation and skills development was positive but severe fiscal constraints limited its ability to drive an economic recovery, and the private sector was still in "wait-and-see mode."
"What you are seeing so far is not enough to change the macro picture. It's the scale that's the problem," Lings said.
Trudi Makhaya, an economic advisor to Ramaphosa, said South Africa was encouraging investors to "come in at the bottom, find affordable assets and develop them."
In his bleak medium-term budget last week, Finance Minister Tito Mboweni slashed this year's growth forecast to 0.5% and showed government debt would shoot up to more than 70% of gross domestic product by 2023.
Afterwards Moody's placed South Africa's last investment-grade credit rating on a "negative outlook".
A downgrade could trigger billions of dollars of outflows from South African government debt.