Perhaps things have changed since I last upgraded my home network, but iirc, advertised wifi speeds are half duplex, while wired speeds are full duplex — i.e. wifi speeds are for the combined upload/download while wired can go full speed in both directions.
It's even worse, because wireless is basically a hub. Or phrased differently: there is only one wire available for all devices on a wireless network, and your (as well as others on same frequencies) devices have to figure out which packet is for which device by themselves.
