Have you followed this thread:
Excitech Cnc Router Purchase
These guys are all buying from a company called SH-CNC in China and are getting pretty good machines.
I would be careful about some of the eBay ads, some of them have feedback for selling sunglasses etc.. however they have never sold a CNC machine!
I would check all feedback first and then contact the customers to make sure they received CNC products and services promised.
Several people have paid for and never received the CNC router they ordered.
Be careful of deals that sound to good.