For whatever it’s worth, you can see my post at Doing a motherboard transplant to upgrade my NAS - #25 by MarkHoltz on the cost of the hardware for a fairly modern CPU (i7-14700k) from my perspective in USD. Unfortunately, the big cost was the motherboard that supported ECC memory.
Do you need to spend that much money when starting out? No. You have to define what you are going to do. If I was personally starting out again, I wouldn’t touch anything less than DDR4 ECC memory.