There are going to be cases where it's more expensive or less expensive at present. One important thing to recognize is that AI doesn't have to do the job better if it can do it much cheaper. We might see a replacement of competent humans with less competent AI at scale because it's just cheaper, which I think would be a bad outcome.
On the other hand, I think we have to think about where this is all headed because it's going there very fast in a few years. I think within a few years, we will see AI that is an extremely competitive replacement for most human labour. That is the premise on which these investments are being made. The massive investments to build AI are justified by the belief that this, in fact, will or at least might lead to the creation of something like superintelligence like we've been describing here.