For hom much can i sell my iphone 4s and buy an iPhone 6s?

I know that the 6s hasn't been released but I was wondering for how much can I sell my iPhone 4s locked on orange 16GB?
And how much would it cost to get a new IPhone 6s?

Not sure how much the IPhone 6 will be but most IPhone 4S 16gb in good condition with charger etc… Sell for about £100-£130 where I live. I buy and sell phones, games, laptops Etc… I'd say for a decent condition IPhone 4S your looking at £120

Ind 10000 selling price of 4s

See:
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Apple also recently boosted the trade-in values for the iPhone 4 and the iPhone 4S. Apple Stores now offer up to $99 toward a new device for an iPhone 4 and up to $199 for an iPhone 4S.