Before spending a lot of gold on your monk weapons, check out this video if you're planning to use a dual wield sweeping wind cyclone build. Here you will learn a bit about the how and why people like to use a Won Khim Lau.
Don't feel like you have to have a Won Khim Lau. For a build like this they really are great, and sometimes you can even find a pretty good deal on one. However it is often times much easier, and much cheaper, to find a simple rare weapon instead at a lower price. Watch the video to learn more.