The memory module on those lists from CPUs Expert doesn't exist. They also link to a single module even thought the part picker specifies 2x4GB. Those are details you obviously have to double check before clicking order anywhere. I think it's hard to find 2x4GB @ 3000MHz below high 90's quid, or a bit over €100 (€150 on that specific site). You
can squeeze in under €600 if you buy at Amazon. That obviously also means more problematic customer service as their office is "UK-based" (in Dublin).
(I tested to put one together at amazon with a Gigabyte Z370 motherboard (because that product was cheaper at Amazon than any H370's
), 2x4GB ADATA 3000MHz RAM, the cheapo i3-8100, a not too terrible Silverstone case, a 500W EVGA PSU, an ASUS Dual-GTX1050ti 4GB and a 1TB Seagate hard drive. It clocked in at €583.
More edits: Just to clarify why I'd suggest a minimum of a H370-based motherboard is because the B360 chipset memory support maxes out at 2,666 MHz. It just happened to be a Z730 on the list I randomly picked as there is apparently a discount on that board on Amazon today. Z370 boards comes with all the bells and whistles, like support for RAM up to almost 4GHz, and it comes with an excellent DAC for headphone bliss, too.