I must say it must be around the 25 Grand mark... Considering the fact that 16GB ones are going for around 20 Grands +, at least here in Lahore...
But I've a humble advise, instead of buying that old junker (its a 3 year old phone, after all...!) why not get a BRAND NEW Android...?
Lots of great phones are in this price range with Full HD Displays, 3 Gigs of RAM or more and powerful 64-Bit processors...
It just beyond me to understand why someone would even consider a TINY LITTLE 4 Inch phone that also happen to be a USED one for 20 Grands and more...???
I know its an Apple, and don't get me wrong, I love iPhones... But only new ones make sense, not ancient junkers which have endured years of abuse, and the batteries on their last breaths...!
iOS 10 runs quite crappy on iPhone 5S, Google it up... And even though it'll likely get the iOS 11 update, the features won't be on par with the latest iPhone...!
If you want a good phone, consider The Google Nexus 5X... I've bought one about two or so months ago and its as smooth as any iPhone ever will be, and guess what, an update to latest Nougat is available on my phone...! And it'll also receive the next Android 'O'...
If you are going for iPhone solely as a ticket or perhaps a medium of 'status symbol', forget the 5S...! Get The iPhone 6, instead... My cousin has one and it definitely draw some stares here & there primarily because he LOVE to flash it around...!
But if you want productivity, experience & performance, nothing is better than The Google Nexus 5X in this price-range, period...
I used to have a Huawei P8 Lite, and I sold it in just few months, then I got The Nexus 5X and couldn't be more happier... In the past, I've had a Samsung Galaxy and an HTC, so I'm speaking with some facts here...
Good Day!