You can find many Go photographs from the Mainichi Shimbun here (with great thanks to kokiri and his 2009 post on SL).
The site shows relatively low resolution thumbnails (which can be extracted with screenshot) and offers to sell their full-resolution originals. They also supply higher resolution photos with watermarking.
Apparently there are also very old photographs if one scrolls down far enough. They can possibly also be accessed by date searching; I haven’t tried. Anything published by a Japanese newspaper before 1968 is, I believe, now in the public domain (which is, ofc, not to say that you won’t still have to pay).
Yes, that is precisely what they are aiming to sell, commercial licensing of their stock photos.
These prices are fairly typical for commercial stock photo licensing. Businesses like this usually don’t even bother to address the minuscule personal use market.
This is common practice for stock photo pricing. Since the license can legally restrict the type and size of the audience, the intended application and medium differentiates the product. However, taking a larger view, I agree that the whole system is quite bizarre, an artificial scarcity incongruous with digital content, but what they are selling is permission, not a physical product.