I also challenge the notion that higher pay leads to less corruption. If so, then why are Denmark, Finland, New Zealand and Norway ranked higher in the corruption perception index[1], when they are paid much, much less annually (especially Finland)[2]?
[1] https://www.transparency.org/en/cpi/2022 (https://archive.ph/fabjP)
[2] https://en.wikipedia.org/wiki/List_of_salaries_of_heads_of_s... (https://archive.ph/XGbpO)
Of course it's hard to find the "actual corruption" figures, but that doesn't mean the perceptions index is of any value.
These are surveys, so there's a limit to how reliable their results can be. However, I find surveys are a pretty good start when you need to get a general idea on how something does and you can't just measure it. How you value that is up to you, that's why I quote it in my comment.
But on this particular index, I strongly suspect it is simply continuing existing biases. It's the thing people quote and by quoting it you get reinforce next year's rankings. Plus it's the kind of thing nobody can ever verify due to its nature.
On a side note, it might be interesting to see the evolution of this index over the years for any given country; that might lead to interesting conclusions on the bias confirmation you're talking about!