Depending on which one you get, 3rd party grey set ones can cost only around $600. Wide angle converter are pretty bad, even if you get the best one the image quality is no where near a real wide angle lens
btw, the UWA is not 2k (for crop body at least), for 3rd party ones, you can get brand new sets at ~$800 or 2nd hand ones at $500-$700. If the wide angle converter is so good, why would others make UWA lens?
Just right on top, as a sticky thread: http://www.clubsnap.com/forums/threads/477934-Using-Wide-Angle-Tele-Converter-on-your-camera
Read and see whether you want to add such thingy to your lens with the obviously horrible effects on your image. Dedicated wide angle lenses exists for a reason and you can get them much cheaper than $2k. Beside this, this converters are used by certain sales men to rip off unknowing people. I have seen offers of $200-$300 and there was even a joker here trying to sell such an adapter for roughly $1k. (Guess he got horrible ripped off and tried to push the damage to somebody else.)
If you die die want to have one just browse Buy & Sell, there are plenty of offerings. Don't pay more than $60.