I just checked, I'm not sure where you found that item on Amazon for $346 but that's a great deal! Read the description carefully as it may be refurbished or an incorrect listing, though. As far as what I'm seeing as standard pricing, Chronocoin is about on-par.

http://chronocoin.com/index.php/samsung-electronics-840-pro-series-2-5-inch-512-sata-6-0-gb-solid-state-drive-mz-7pd512bw.html is $539

http://www.serversupply.com/products/part_search/pid_lookup.asp?pid=191781&gclid=CO-ApNyG_LYCFceDQgod3gEAFQ $530

http://www.memory4less.com/m4l_itemdetail.aspx?itemid=1468453021&rid=94&origin=pla&gclid=CKbg5uiG_LYCFQ5xQgodiTEAGQ $699


http://www.newegg.com/Product/Product.aspx?Item=N82E16820147194 is $519

http://www.amazon.com/Samsung-Electronics-2-5-Inch-SATA_6_0_gb-MZ-7PD512BW/dp/B009NB8WTI is $484