As of August 2015, the cheapest website to buy a Samsung Galaxy s4 is eBay. The Galaxy S4 is available on eBay.com for anywhere from $90 to $185.
While eBay may be the cheapest website on which buy a Galaxy S4, it may not be the best option. A phone purchased on eBay often has no warranty, and it may have sustained damage at the hands of its previous owner. These issues can be minimized by checking the feedback of eBay vendors. Members with high feedback ratings are tried and tested merchants whose merchandise and customer service is likely to be reliable.