Have you seen a Gursky Photograph in person? Criticizing a photo of a photo of an artist that you don't know is a very bad way of judging without reason in a completely subjective way.
I understand how shocking is to see a photo like this and hear that is valued in this much money but as Fustian said, is all about supply and demand.
Let's say you don't like it which is your personal taste and you obviously have all the right to not like it. But once you see his art work in person you might change your mind and if you don't at least you will know that it is such a perfect technical execution in very hight quality materials that you will know that is it worth a lot of money. Then when the artist has a limited edition of 6 and he becomes the hottest photographer in the world, then you will understand why people are willing to pay such a hefty amount of money, which by the way, I'm totally blown by the fact the one of his artworks has reached $4.3 millions.
By the way, this is not even a panorama photograph. And good luck to your grandma in producing this size and quality:
chromogenic color print face-mounted to Plexiglas
image: 73 x 143 in. (185.4 x 363.5 cm.)
overall: 81 x 151a x 2 in. (207 x 385.5 x 6.2 cm.)
This work is number one from an edition of six.