Those are nice options, the HPE MicroServer Gen10 Plus (the 8GB + G5420) is around 800$ (E-2224 + 16gb is around 1250$) here and the T340 (16GB with E-2224) are around 1500$. Not that unreasonable but still a little too much for me to spend that instead of using what I have, at least for me and both of those might not meet my performance requirement for additional stuff I want to do on that machine as I mentioned.
Mini XL+ would be around 2200$ Including taxes and shipping xD
Unfortunately, prices here are usually higher and also have 23% VAT which as you can see, pushes the prices quite a bit higher than what you might think they would cost.
The server/enterprise market here is rather bad. I had to import the HBA from china for 45$ (They usually do not add tariffs and taxes to those from china) as the cheapest equivalent of that SAS or similar here costs like 120$ (I would have to flash IT on those) or 150$ for those that are already flashed or are IT by default.
Asrock x570 is around 500-600$ new, x470 is around 350+ and there are no used ones on the market here xD
For the CPUs, I have 3900 or 5800x3d as options (do not want to buy another cpu). 5800X3D is more power efficient than 3900 so I went with this one for the build. It is not like I bought it specifically for this build, I have it (and the other one) as I use them to test my software as I mentioned before too. I need different architectures and generations as I write software that is trying to maximize performance on many of them using all instructions and need it to measure real-life performance. Different instructions, e-cores (12th gen), different amount of cache, cores per ccx (amd, zen2, zen3) with different real-life performances with SSE, AVX2, and (V)AES. This is why I also said that NAS will go down a few times a month as I still need the CPU for the tests.
When I was choosing mobo for the 2nd CPU I went with one that I knew supported ECC as I was also thinking about potential usage as a NAS. I might have to think if I want to spend 350-500$ on the AsRock Rack MoBo just for potential components difference and NIC (but worse PCIe configuration).