During early Christian times, 30 pieces of silver was the going price for betrayal. In our own inflationary era, the price has gone up -- even as high as $390,000 a year.

That's the price the South African government is paying William A. Keyes to persuade black Americans that apartheid is not such a bad thing.

The South African government's propaganda effort is not so shocking. What is shocking is that Keyes is a black man.

Since August, Keyes, a 32-year-old American, has been a lobbyist for the white-controlled government of South Africa. In that capacity, he has arranged meetings between black reporters and high-ranking South African government officials, appeared on American television to support President Pieter W. Botha's racist regime, and tried to get black American business persons to set up shop in South Africa.

Last month, after Winnie Mandela, wife of jailed South African leader Nelson Mandela, said in a taped interview on Cable News Network that "total" U.S. sanctions were needed to end apartheid, Keyes was in the studio to denounce the African National Congress, which Nelson Mandela once led, as "a terrorist outlaw organization."

In an interview with Washington Post reporter Juan Williams, Keyes, a Republican, said he has no qualms about his work. "One of the first things I do is to remind people that South Africa is not just a political issue but a country that has people in it . . . . "

But Randall Robinson, leader of the year-old Free South Africa Movement demonstrations, said Keyes' lobbying efforts are "incredible . . . . For money and out of some profound self-loathing, a very few of the subjected always participate in their own humiliation. It was true in Nazi-occupied France, it was true throughout the colonized world, and it appears to be true in the case of Mr. Keyes."

Moreover, people all over town are asking how in the world this man can try to sell them a government that 14 months ago adopted a system denying political rights to 24 million blacks. So far, the violence resulting from that decision has killed 850 people.

One of the reasons the South Africans want a black lobbyist is that the black-led antiapartheid demonstrations have hurt South Africa financially. President Reagan has imposed limited economic sanctions against the country and forbidden the sale of the South African krugerrands.

Meanwhile, protest leaders continue their activities, planning a special demonstration on Thanksgiving eve to mark a full year of demonstrations.

Keyes, however, is unmoved by the swelling opposition to apartheid.

"One-man, one-vote is the principal question only for activists outside South Africa," says Keyes. "The principal question to men and women in South Africa is . . . whether they will be able to provide for themselves and their families . . . . After they deal with that, political participation comes into play."

But many South Africans disagree, insisting that economic issues cannot be separated from political issues for black South Africans.

"The homelands are tribal death cells," a South African woman told the U.N. international women's conference in Kenya in July. "The lands are not fertile, and there are only hungry women and children with no health facilities to speak of."

Said another: "We are not citizens in our own country. We see our husbands only two weeks a year, and the homelands are like concentration camps."

Said the Rev. C.R. Beyers Naude, a white South African, upon receiving the Robert F. Kennedy Human Rights Award here last week, "No solution is possible as long as the white minority clings desperately to the power it has drawn to itself . . . . I am addressing myself to my people, the Afrikaners . . . . Your day of domination is over. Your day of liberation is dawning . . . . "

Last Thursday in South Africa, police fired on a crowd of 25,000 black demonstrators, most of them women, killing several and setting off a stampede in which hundreds were hurt.

While their families are mourning, Keyes sits in his Washington office, making more than $1,000 a day, and looking to the future.

"In the next few months, when I start representing the South African government on the West Coast," he said, "my contract will reach the half-million mark."