All I can say is that I agree with the previous posts that the wobble you experience (I'm still not sure what you mean by it) has nothing to do with any plastic worm gear. If that fails, the beater doesn't rotate.
Is yours a tilt head model? If so then that wobble is probably the tilt joint failing, and that is going to be a weak point in any tilt head mixer (one reason why I bought a bowl lift model). If the wobble is in the beater drive, then there is a bearing failing or something in the drive train.
In my opinion, you are still way ahead buying one quality tool over buying several cheap ones. I was a machinist for more than 30 years, and the tools I bought as an apprentice were still in my tool box being used when I retired. There is simply no way that a cheap tool offers more overall value than a quality one. From all I've read, KA is pretty good about standing behind their products, and they have responded favorably to the issues which resulted when they did try to cut a few corners.