These prices pretty much put the Lumia 950 XL against Apple's iPhone 6S 16GB version which is priced about the same in Europe, around €739-759 depending on the region.
In case you missed it earlier, the lower priced Lumia 950 will pack a 5.2-inch 2560x1440 display and be powered by Qualcomm's Snapdragon 808 SoC with 3GB of RAM, 32GB of storage and a 3000mAh battery. The more expensive Lumia 950 XL features a larger 5.7-inch 2560x1440 resolution display, Qualcomm's Snapdragon 810 SoC, 3GB of RAM, 32GB of storage and a beefier 3300mAh battery. Both smartphones are expected to have a 20-megapixel PureView rear camera and 5-megapixel front one.
At these prices, Microsoft will have quite a hard job in snatching customer from the competition but bear in mind that this is an early listing so prices might change when Microsoft officially announces its new flagship Lumia smartphones.