wifi - why so exepensive?

Is it really cheaper to make a wifi interface for an Arduino from a Raspberry Pi and an Edimax usb wifi dongle???

Or for an even cheaper route, use an Edimax wifi router/repeater (less than £20) and stick OpenWrt on it???

Seems all wrong to me?

I'm guessing there is all sorts of regulatory hoops you have to jump through to certify a wi-fi interface. I know I've seen reports about cell phones that the radio modules (which I think does all of bluetooth, wi-fi, and cell communication) is about $20. The rest of the cost is for the red tape.