exchange

depends on when it was bought, condition etc. Try flipkart, Amazon once to check ( it will be more than 50% depreciation for sure on these websites)
another website to check selling price is Cashify.com
i suggest selling on Olx/Quickr to get good value

almost all exchange on all products by retail or ecommerce agencies do value will be calculated this way

PRESENT MARKET PRICE - almost 60% or higher = EXCHANGE VALUE

i.e. if the price of device is 500 and present market price is 430 than your exchange value will be

430 - ( 500 × 60/100 ) = 130 ( maximum)

in case scratch , color issue , battery life calculated than from the miximum value additional perchantage will be reduced

You will get on average maximum 15 to 17 thousand exchange value