the MiktroTik CRS305 is pretty unbeatable @ ~$120 USD but it's SFP+, if you're looking for RJ45 then about the only thing even relatively cheap is the Nighthawk SX10 but it's only got 2 ports and costs twice as much. I thought about both but never gave them a go, though.
if you have spare hardware laying around, why not throw in an Intel X540 or a Broadcom 57810S and make a switch? I'm doing that with my NAS, it doubles as my 10 GbE switch. If you need/want more 10 GbE ports later, throw in a 2nd/3rd/20th card later.
The X540s can be had (used) under $100 and the 57810S are under $40 (used), both come in either SFP+ or a RJ45 flavor. I got 4 57810S for under $100 shipped and an X540 for $70 not that long ago but the 57810S don't play nice outside Windows Server or Linux.
you can either go the pfSense route and be the incarnation of r/homelab or be lazy (like me) and stick with Windows. I have it set up so that the only time the 10 GbE portion of network is being used is when I'm accessing my NAS, otherwise it uses the onboard NIC and goes through my router. That way when/if my NAS goes offline the rest of my network doesn't lose internet. Just put the NIC on a different subnet and IP range and set the gateway of each NIC on a machine to the IP of the NIC it's attached to on the other end.