I have just bought a $30 wireless router which claims a transfer rate of 150Mbps.
Can that really be true? Or is this with an assumed compression or some other marketing fine print?
There's no reason it can't use the 150Mbps protocol in 802.11n. Just keep in mind that like all other current wireless technologies this speed is unswitched half-duplex. It's nowhere near as good as the same 150Mbps would be in a wired network. Also, like other wireless technologies it's susceptible to interference and airspace conditions. The 150Mbps is a theoretical max that is seldom reached (again, unlike wired networks, where published speed is often is the actual speed).