How much money needed to replace iphone

Hello all,

I have a iPhone 4s with greyed out problem. My phone had a water damage but it did not cause anything on the phone. However, 2 weeks ago my wifi just greyed out. I cannot use wifi anymore. What I am wondering is, how much money do I need to replace the phone ? I saw 150€ and 150$ to replace. I suppose Apple gives the "0" phone to customers after the payment but I want to be sure on the amount of the money ? Does anyone has an idea on that ?

Thank you.