You're right, if there's no need of GPIO. For example I'm using a Fujitsu Futro S720 that I've bought for about 30/40€ and it consumes about 4W idle and 10/15W maximum (I don't really remember). My point of view is like yours: those boards are not good for self hosting, are good for IoT, digital signage and...mmm...I don't know what else.