reductions in / of

[CaseyA]

In a study conducted by my colleagues at the University of Minnesota, large reductions in the price of healthy snacks did not necessarily lead people to substitute a more nutritious snack for a less healthy one.

What is the difference between "reductions in" and "reductions of"?

[Raymott]

What is the difference between "reductions in" and "reductions of"?

They are commonly used like this: "There has been a reduction of 10% in the price." That is, "There has been a reduction in the price of 10%."
"Reduction of the price" is not wrong, but it's also not common. "Reduction in 10%", of course, is wrong.