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Just don't go to a Carrier. Verizon is still selling the iPhone 5s for $50 more than the SE. Doesn't make sense.

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eBay might be a good place to look.

On eBay I sold my 5S for about £125 and it even had dent marks on it. Most likely it be second hand but I'm guessing you can get one for about $100-150+ in the US if you look hard enough.
 
If you have a Discover card, 5% off Apple purchases if you access through Discover portal.
 
Pretty much your best bet will be a used iPhone 5s from eBay, Swappa, etc. The iPhone SE was already priced so low that no one can really sell even a 2.5 year old iPhone 5s for less than what the SE costs.
 
Looking for a new but discounted 5S. Anywhere I can purchase?
I bought my 5s from eBay, it's refurbished and came in new box with all new contents and the phone looks brand new, not a mark on it. I am really happy with it.

Edit: forgot to add it cost £150
 
Looking for a new but discounted 5S. Anywhere I can purchase?

If you are looking for a brand new one with warranty you would have to get it from one of the prepaid carriers, like cricket, boost etc. No major retailer is selling the 5s anymore.
 
check out the prices at gazelle.com

32 GB unlocked $249, att and vz slightly cheaper
 
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