I have the Came one (mine was called the eagle eye 5d but it is the same made by DYS). It is good, but there are a number of fairly huge flaws. The attachment for the camera is very poor, you really need to be able to move it side to side to balance, but you just have a choice of three runners.
All the parts do cost more than $300 individually, it uses the alexmos/basecam 8bit controller (£100) and the three motors are larger than standard and are about £30 each. Plus all the carbon tubes and so on (difficult to find a cheap source for) they are probably at the cheapest they will get (mine was £500). However, the new 32 bit alexmos/basecam controller will make them much better, they have two sensors so they can be used in a wider range of movements without oscillation and won't be as pedantic with settings. So I would say wait for the next round of cheap knockoffs.