It is really funny to read that in the beginning of 21-st century, some young people may think that journals and books printing had something to do with typewriters:-)
If you look attentively at the page you scanned you will easily see that this is not a TeX font and not a typewriter. It is more beautiful.
Before the middle 1990s we lived in the "Gutenberg Universe". In the universe where everything was PRINTED using lead fonts. This was the case from XVI century to th 1990s. The authors (Heisenberg, for example) would submit their paper to the journal, HANDWRITTEN, or text typed on a typewriter, and formulas inserted by hands. Until the beginning of 1990-th mathematicians inserted formulas by handwriting in a typed manuscript.
Typewriters which could type Greek and Latin letters, and some formulas were common only in the US, and even there I am not sure how common.
This handwritten manuscript would go to a typography. There professional typesetters would make "pages" composed of lead letters (they had thousands of fonts in good typographies). Typesetters in the beginning of the 20-th century took these letters (made of lead) from boxes, and connected them together
into lines and into pages (called "matrices"). These lead blocks called "matrices" contained mirror images of pages, one of each page. They would be used for printing, then the output was
sent to the author for correction, then corrected and sent for correction again,
In 1960s I visited such a print shop. Printing the local newspaper. The labor condition were terrible: enormous noise, lead dust everywhere... This was a very hard work. And take into account that the
typesetter had to compose lines right-to-left. Some mechanization was introduced later, like the machine called linotype, (see "Linotype machine" in Wikipedia) which was something like a typewriter but enormous. And only professionals worked on them, not the authors, not Heisenberg:-)
As Gerald Edger commented, typesetting mathematics was a very expensive task which required most experienced typesetters. Printing anything was very expensive, especially math.
So it is really strange that the prices of mathematical books and journals
skyrocketed AFTER the journals switched to TeX. Nowadays the publisher has practically nothing to do: the major expense of typesetting has been eliminated.
Added remark: whatever the publishers do nowadays, before 1990s they did the same AND typesetting in addition to this. And now compare the prices, just out of curiosity. At least in 1980s many good universities were able to afford subscription to all or almost all math journals.