That depends on your area. These machines are not available new (at least not at a reasonable price) but they are readily available refurbished for around 35€ (4gb ram) to 50€ (8gb ram) per piece in Germany.
I have a Unifi router (Unifi cloud Gateway Fiber to be precise), which one you could argue is on the higher end of consumer hardware. But there are also more consumer oriented routers with that capability.
I am certainly not an expert by any stretch.
But here are my reasons:
Ability to isolate some “sketchy” IOT devices into an IOT only vlan, where they are not allowed to access the rest of the network, only the internet and incoming traffic from the other vlans.
Having a “clean” vlan/subnet for servers and services where I can give out static IPs without worrying about collisions with client devices
I attempted to move my whole 192.168.x network without vlan to a new 10.x network with vlans. I am still tracking down services and devices where I hardcoded in the old 192.168. ip adresses.
There are ready made modules for it that slot into an unused PCIe slot into your case. They are available on aliexpress, search for „tuya WiFi pc power switch)
But I have multiple devices and want to access it from all of them.