I wonder though how much of science has similar issues, that there are hundreds of semi-promising but niche areas that require tons ton of deep analysis that would have simply cost too much to explore all areas, but now become feasible.

The Navier-Stokes proof cost ~10mio USD in tokens at consumer prices, and it was something that the two people working on it were allegedly weeks or months away from solving. You can buy ~200 Math PhD Years for 10Mio USD, so it doesn't seem like a shortcut at all (actually it sounds like we would have gotten the same solution for ~1-0.1% of the price if we had just been a little patient.

We weren't willing to pay for 200 math PhD students to try to find singularities in Navier-Stokes, I am skeptical of how much we would be willing to pay OpenAI to do research on "niche scientific areas"?