You can download the ISO off the Microsoft page and not activate it if you do not mind a watermark, for the OS. No Keyboard and Mouse.
Has a Monitor:
PCPartPicker part list:
https://de.pcpartpicker.com/list/qcj7r7
Price breakdown by merchant: https://de.pcpartpicker.com/list/qcj7r7/by_merchant/
CPU: Intel - Core i5-8400 2.8GHz 6-Core Processor (€194.59 @ Alza)
Motherboard: MSI - Z370-A PRO ATX LGA1151 Motherboard (€111.71 @ Amazon Deutschland)
Memory: G.Skill - Trident Z 16GB (2 x 8GB) DDR4-3000 Memory (€152.74 @ Amazon Deutschland)
Storage: SanDisk - SSD PLUS 240GB 2.5" Solid State Drive (€78.98 @ Amazon Deutschland)
Storage: Western Digital - Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive (€44.40 @ Amazon Deutschland)
Video Card: EVGA - GeForce GTX 1070 8GB SC GAMING ACX 3.0 Black Edition Video Card (€599.00 @ Caseking)
Case: Cooler Master - MasterBox Lite 5 ATX Mid Tower Case (€47.29 @ Amazon Deutschland)
Power Supply: Corsair - RMx 550W 80+ Gold Certified Fully-Modular ATX Power Supply (€90.91 @ Mindfactory)
Monitor: AOC - G2460PF 24.0" 1920x1080 144Hz Monitor (€226.78 @ Mindfactory)
Total: €1546.40
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-01-29 14:41 CET+0100
46 Euros over, but has everything you need. Strangely, found 16 GB of DDR4 RAM at 3000 Mhz at a much cheaper price than its other 16 GB counterparts of all speed.