'Liverpool will decide what he is worth, not City'
From your wording it seems as though you're talking about the price that Liverpool will sell at. Which is how much THEY may feel he is worth, but ultimately it is just the cost/fee they are selling him for.
By saying City dont get to decide how much he is worth is implying they cant have an opinion on the matter. Which surely you are not suggesting?
And as for you quotation marks on what I'm guessing is a generic quote on what other people are saying, surely there's a purpose for it? Because it seems you are suggesting that only Liverpool can determine what Sterling is worth and other people/clubs cannot, I wonder how you can say that my reply was exactly what you were stating.
I feel you've mixed your words up. Cost/Fee is different to worth. Liverpool/City/You/Me/Fat sam can all determine what something is worth.