Some of the models with good value are (Prices accurate as of 1st Aug 2017): 1) Samsung S8 – $600-$750. 2) S8+ – $650-$850. 3) S7 edge, $450-$600. 4) Sony XZ Premium $500 – $700. 5) Huawei P10 Plus – $500-$700. You might have one of the above models (purchased at a low price on a mobile contract) which you like to trade up!