sorry to interupt, but used prices vary from set to set.
no one can give u an exact estimate of used phones. its just like uses cars.... a city 2005 model u can get from 6 lacs all the way to 8 lacs depending on the condition. something goes with phones.
its better to use ones head rather then trusting the shopkeepers. if u getting a 10 month warranty phone for less then 7-8000 , then ask yourself Y ????
1) many "warranty" phones are actually company claimed as the starting pieces of e7 , n8 , e90, e72 , e51 etc all had varies problems which the company were fixing for free.
2) many metal based phones are also coloured and kept which u will hardly ever notice untill u use it for 4-5 days....
3) almost 85% of the iphones are all repaired in some way or the other. because of the copy charger which we use, it damages the phones which we dont notice in the short run.
a copy charger comes for 200 , whereas the original iphone charger comes for 1200......
and the way the shopkeeper open the phones, anyone hardly notices that its repaired.
4) and then there is the all famous "fake warranty tag" which is available in the market for 5 rupee each. u put in on a phone and ppl will think its not repaired 
5) last but not the least, the warranty itself....... many shopkeepers who import cell phones , are now giving their own warranty.... which is worth basically nothing............
therefore if somone says u brought the phone for 30 and he brought it for 25...... then dont be disheartened, mayb u brought the right phone
