Looks like you're mainly paying extra for the ROG branding with the Radiance. To give you an idea of two systems with and without the branding.
Intel Core i7-13700F (Raptor Lake) Socket LGA1700 Processor - Retail - £359.99
Asus ROG Strix B660-F Gaming WIFI - Intel B660 DDR5 ATX Motherboard - £239.98
Kingston FURY Beast 64GB (2x32GB) DDR5 PC5-44800C40 5600MHz Dual Channel Kit (KF556C40BBK2-64) - £229.99
Asus GeForce RTX 4090 ROG Strix OC 24GB GDDR6X PCI-Express Graphics Card - £1,999.99
Crucial P5P 2TB M.2 2280 PCI-e 4.0 x4 3D NAND NVMe Solid State Drive - £179.99
ASUS ROG Strix Helios Midi-Tower ARGB Gaming Case - Black Tempered Glass - £329.99
ASUS ROG Strix LC II 360 Performance ARGB AIO CPU Liquid Cooler - 360mm - £224.99
Asus ROG Strix 1000W Gold Aura Edition Modular 80+ Gold ATX 3.0 PCIe Gen 5.0 Power Supply - £249.95
Microsoft Windows 11 Home 64-Bit DVD - OEM (KW9-00632) - £127.99
Grand Total: £3,954.85 (includes delivery charge, £11.99)
Intel Core i7-13700F (Raptor Lake) Socket LGA1700 Processor - Retail - £359.99
Gigabyte B760 GAMING X AX (LGA 1700) DDR5 ATX Motherboard - £199.99
Kingston FURY Beast 64GB (2x32GB) DDR5 PC5-44800C40 5600MHz Dual Channel Kit (KF556C40BBK2-64) - £229.99
Zotac GeForce RTX 4090 Trinity 24GB GDDR6X PCI-Express Graphics Card - £1,699.99
Crucial P5P 2TB M.2 2280 PCI-e 4.0 x4 3D NAND NVMe Solid State Drive - £179.99
Phanteks Eclipse P600S Glass Silent Midi Tower Case - Black - £152.99
Phanteks Glacier One 280MP All In One CPU Water Cooler D-RGB Black - 280mm - £129.95
Thermaltake Toughpower GF3 1000W Fully Modular Native PCIE 5 80 Plus Gold Power Supply - £199.99
Microsoft Windows 11 Home 64-Bit DVD - OEM (KW9-00632) - £127.99
Grand Total: £3,292.86 (includes delivery charge, £11.99)