Is money earned from ranking high in search results through backlinks from other websites owned by the same person, in violation of search engine policies, permissible or forbidden?

There is no objection to placing a link for a permissible product on your website and earning from it. However, creating other websites to link to your original site and top search results is impermissible due to the deception, fraud, and misrepresentation involved. This falls under the ahadith that prohibit deceit, cunning, and trickery, and it also violates Google's policy. Therefore, you must refrain from this action, for "sustenance is apportioned."