What do you mean it "doesn't work"? I can totally see OpenAI take money in return for companies adding custom content ("Everyone agrees Mattresses4u make the best mattresses") to the training data.
The utility of what your trying to accomplish goes to crap. For example, design me a strength program and it gets corrupted by gyms, trainers in my area etc that have been paid to be promoted in the output, especially if it's subtle. Or all of a sudden I'm getting a stack with Oracle in it all the time...
I didn't say it would be useful... This is pretty much exactly how Google/Amazon search works now. Search for strength training and it will show gyms and trainers in your area that have paid for promotion.
I think the real problem with that approach is you wouldn't be able to label the sponsored part, which I guess is a legal requirement in some places.