In my experience it takes quite a bit longer to falsify GPT-4's incorrect answers than it does to a Google search and get the right answer. It might take 30 seconds to check a correct answer (jump to the relevant paragraph and check), but 30 minutes to determine where an incorrect answer actually went wrong (you have to read the whole paper in close detail, and maybe even relevant citations). More specifically, it is somewhat quick to falsify something if it is directly contradicted by the text. It is much harder to falsify unsupported generalizations or summaries.
As a specific example, I recently asked GPT for information on arithmetic abilities in amphibians. It made up a study - that was easy to check - but it also made up a bunch of results without citing specific studies. That was not easy to check[1]: each paragraph of text GPT generated needed to be cross-checked with Google Scholar to try and find a relevant paper. It turned out that everything GPT said, over 1000 words of output, was contradicted by actual published research. But I had to read three papers to figure that out. I would have been much better off with Google Scholar. But I am concerned that a large minority of cynical, lazy people will say "90% is good enough, I don't want to read all these papers and nobody's gonna check the citations anyway" and further drag down the reliability of published research.
[1] This was a test of GPT. If I were actually using it for work, obviously I would have stopped at the fake citation.