I have seen wheeled ones for sale in Europe, and they run like 600 euros.
If you are handy and patient you can build one, for waay less. I spent a little over $200 to build mine.
Here is a link to my short build thread:
http://www.rctruckandconstruction.co...ighlight=delta
I have since put in faster motors, and it's working great. The pololu motors are stronger than the tamiya gear boxes, and they run at 6 volts, the same as the servos, receiver, and motor controller, which keeps it simple.