https://aliexpress.ru/item/1005003911721041.html?For $50 you can buy a motherboard for 8 video cards, a processor and a cooling system for the processor, and your device costs $30. Goods from China can take 45 days, but if you order in advance, then this is a good and proven motherboard.
Did you use this motherboard yourself?
It looks like a good deal at US$60 including shipping, but I
found one that supports 12 GPU's for $90. However, it doesn't include a CPU, which will cost $30.
So I have to choose between $60 for 8 GPUs (30 day wait) or $120 for 12 GPUs (5 day wait).