Taxis in Kunshan are usually everywhere; that is, of course, until you desperately need one. Rush hour time in Kunshan, about 4pm-8pm, is very hectic, and you may need to aggressively wave down a taxi. If you don't, someone else certainly will, even if you're first in line for it.
Also, though it's not common, DON'T LET ANY TAXI DRIVER PICK UP OTHER PEOPLE DURING YOUR RIDE. They may try to do this during busy holidays, and may try to charge you for any other traveler's fees, as well.
In my experience, here's the cost for traveling between different areas:
Downtown Kunshan to Kunshan South Station ---> 20-25rmb
Downtown Kunshan to Shimao ---> 25-30rmb
Downtown Kunshan to Yangcheng Lake ---> 60rmn-90rmb
Kunshan to Shanghai ---> 300-400rmb
Kunshan to Shanghai Pu Dong Airport ---> 400-600rmb
Kunshan to Suzhou ---> 150-200rmb
There are a few routes that will even take you all the way to Yangcheng Lake.
In addition, if you're ever stuck in a long line waiting for a taxi at Kunshan South Railway Station, just try hopping on a bus.
A Bus Station is located at the back end of the railway station.