This is interesting, Aldi, the discounter, is selling the iPhone X 64GB for 349€ on its Aldi-Talk plan (run through Medion Group).
The phones aren’t new, they are refurbished - they take the old phone dismantle it, check and replace any defective components, then re-assemble and polish the device. At the most it should show minimal signs of wear (no scratches longer than 0.5mm in length).
They provide a standard 2 year guarantee with the phone. They are also throwing in a Qi charger, along with all of the original accessories (cables, headphones, power adapter etc.)