I make no claims to be a pro at this, but I have read that certain things like the famed "gli" and the sound of "gn" are kind of sounded a second time when following vowels in the middle of the word. So saying "ognuni" would be the proper way according to that.
My resource is Barron's Italian Grammar.
I think it's like saying I want to get more out of it. Like how we say 'I want more bang for my buck'. Ogni is not each, but every. In some cases, each and every are interchangeable as many words in English are, but this seems to occur a lot less in Italian than it does in English.
More of something, for example, money, for every kilogram. I could offer an amount for the first kilogram, but want to offer less (per kilogram) if I take 10 kilograms. The provider does not want to accept less, so they "want more for every kilogram."
That's how I interpret it