Cheap USB WLan Stick

Hello,
I am looking for a cheap wifi solution for my arduino. I am new at this whole arduino stuff =)
I found a few wifi shields for about 50-200$. Why are they so expensive?
A foobar-noname (ralink chip) usb wlan stick is about 5$.
Isn’t it possible to use an old ralink usb wlan stick with the arduino?

Not as is, no. The Arduino per se can't act as a USB host (there are software solutions but afaik, it's only suitable for mice, keyboards and that kind of simple USB-stuff).

People have successfully interfaced the Arduino with USB mice, keyboards, digital cameras, etc., but it won't be cheap:

http://www.solarbotics.com/products/18890/

Microchip now has cheap (< $5) small microcontrollers with USB host capability, and I asked them about whether they were capable of driving things like the cheap WLAN and Bluetooth dongles that are available. The short answer was “probably not.” The reason that these things are so cheap has a lot to do with putting really minimal hardware in the stick, and putting a LOT of support software in the PC-side drivers. An arduino (or the PIC microcontroller with the USB-host capability) just doesn’t have enough memory to do the equivalent…

I haven’t looked really carefully to see whether I entirely believe this, but it makes some sense.

(OTOH, this doesn’t adequately explain why you can buy a complete linux-running wireless router for less than a “wifi shield”, but that has more to do with the economics of mass production and obsollesence. I think.)