For those prices I could buy an old PC to do out of band management and have over half the money left over. The appeal of JetKVM/NanoKVM is they're price competitive with an extra PC for a tiny fraction of the physical and power footprint.
I'd assume it runs off the 5v standby power when the primary ATX supply is sleeping. =3
Small recycled PCs can certainly work too, and reminds me of the https://guacamole.apache.org/ project. =3