It doesn't matter whether he had any influence over the fee or not. Rooney did not influence his. Ronaldo did not influence his to Real. WE (Manchester United), however, had an influence in what we paid for Fellaini. Our price should reflect what he is expected to offer. Whether or not he is considered a waste of money will be assessed by his contribution.
I've heard this theory of yours a few times and I think it is so obviously flawed, and genuinely can't believe people still use it. Would it be okay if we broke our transfer record to sign Buttner? After all, we had a need for a back-up left-back in the squad, and that's what he gives us. The fee is irrelevant, and had nothing to do with him, he's just here to do his job of back-up left-back after all.