Like you, I have no idea why I should need a rank to buy something, is there something on earth that can not be bought with money? Perhaps a noble title, and that, I also doubt it. ..
And here's proof, that you actually CAN buy a noble title.
Snip from Wikipedia:
Adult adoptees and "knights"
Together with Gabor, Anhalt has himself adopted at least ten adult males. "If someone offers you $2 million, you do it," he is reported to have said.[8]
Frédéric Prinz von Anhalt adopted several adults:
Michael Prinz von Anhalt (birth name: Michael Killer)[11]
Marcus Prinz von Anhalt (birth name: Marcus Eberhardt), also calls himself "Prince Germany";[12]
Oliver Prinz von Anhalt (1971-2016, birth name: Oliver Bendig)[13]
Markus Maximilian Prinz von Anhalt (birth name: Markus Chapelar)
Albrecht Alexander Prinz von Anhalt (birth name: Alexander Wessel)
Ferdinand Prinz von Anhalt (birth name: Markus Wölfert)
Alex Prinz von Anhalt (birth name: Alex J. Anaxagorou aka Alex the Greek)
In addition to selling his name in marriage, Anhalt has sold as many as 68 "knighthoods" for $50,000 a piece.[7]