homelab

So with Crypto mining being less profitable and miners selling their rigs for cheap I thought how can I get my self a cheap managed network switch. I saw mining motherboards with 12 PCIe 2.0 1x slots(4gbit bandwidth) and tought hey if I plug in some cheap 10g 2port network adapters I can make my own network switch with exactly the ports I need(SFP+ rj45). Put opensence on it and boom Managed network switch with multigig(2gbit per port). Is there something I am missing or have I found a way to get cheap multigig? Also can anyone who has a 10g only network switch tell me what kind of power it is using per port so I can compare? Thanks for debunking my idea and saving me a few bucks.