We’ve turned into a Hive, things are getting serious.

So why do we sometimes see couples where an elf/elf maiden 10/10 is with an orc/orcish man 3/10? And these orcs are just ordinary people, not some super-successful businessmen with billions in the bank. With the latter, even with a -1/10, elves would be 100/10.

You are right about the last point; an orc can buy an elf maiden with money. But the elf maiden will still want an elf. And if the orc is stupid, the elf maiden will also take some of his money and leave for an elf. Or she might just cheat on him with an elf; there can be different variations.

where an elf/elf maiden 10/10 is with an orc/orcish man 3/10?

According to the same statistics, women of ordinary men who are rated 5-6 rate themselves as 3, so))) A 3 is a person like Elmira the incel. I highly doubt you've seen many such people with elf maidens 10/10.
But an elf can definitely be with an orcish woman. That's the point; men are less picky, due to the same biological reasons.