Per the article, the critic for the critic is human RLHF trainers. More specifically those humans are exploited third world workers making between $1.32 and $2 an hour, but OpenAI would rather you didn't know about that.
OpenAI may well still be employing plenty of people in third world countries for this. But there are also contracts providing anywhere from $20 to $100+ an hour to do this kind of work for more complex prompt/response pairs.
I've done work on what (at least to my belief) is the very high end of that scale (not for OpenAI) to fill gaps, so I know firsthand that it's available, and sometimes the work is complex enough that a single response can take over an hour to evaluate because the requirements often include not just reading and reviewing the code, but ensuring it works, including fixing bugs. Most of the responses then pass through at least one more round of reviews of the fixed/updated responses. One project I did work on involved 3 reviewers (none of whom were on salaries anywhere close to the Kenyan workers you referred to) reviewing my work and providing feedback and a second pass of adjustments. So four high-paid workers altogether to process every response.
Of course, I'm sure plenty lower-level/simpler work had been filtered out to be addressed with cheaper labour, but I wouldn't be so sure their costs for things like code is particularly low.
Exploited? Are you saying that these employees are forced to work for below market rates, and would be better off with other opportunities available to them? If that's the case, it's truly horrible on OpenAI's part.
https://time.com/6247678/openai-chatgpt-kenya-workers/