The new Prime Edition replaces core components of the original One M9 with a MediaTek SoC, weaker rear camera, slower LTE connectivity, and less RAM for a more affordable starting price.
http://www.notebookcheck.net/HTC-One-M9-Prime-Camera-Edition-coming-for-430-Euros.160956.0.html
Thanks for the great article and information. I have read somewhere that the memory is expandable to 2TB (http://www.mobiblip.com/htc-one-m9-prime-camera-edition-launched-price-specifications-and-features (http://www.mobiblip.com/htc-one-m9-prime-camera-edition-launched-price-specifications-and-features)). Please clear this if this is true.