It can hardly be more affordable than a Redmi 9A. However, you have to accept some compromises when purchasing the low-budget smartphone. Perhaps too many compared to the Redmi 9 or Redmi Note 9 sibling models ...
https://www.notebookcheck.net/Does-the-Redmi-9A-reveal-too-many-compromises-in-the-test-compared-to-the-Redmi-Note-9.504073.0.html
Regarding 1st world countries, this is more than enough for a grandma.
Regarding people with extremely tight budgets... 20 € might be a week's salary.