Many styles and sizes of cheap drum sets can be found for sale at any given time. Keep in mind, that the term 'cheap' generally refers to price, but also consider the quality that you are looking for as far as your experience and needs require. A beginning drummer may be looking for a cheap drum set because they don't really want to invest alot of money into something that they're not sure if it will be something that they will still be excited about in 3 Months time. The same will hold true for many parents searching cheap drum sets for their kids, (the excitement may pass, and they don't want to invest a bunch of money into a passing phase.
The other side of the coin is the experienced drummer who just basically wants to save some money while picking up a new kit, or maybe buys cheap drum sets to clean up, tune, dress up and re sell for good profit. This is pretty easy to do as you can pick up cheap drum sets that are complete sets, and maybe upgrade the cymbals or hardware, add new skins, or any number of simple things that can greatly increase the value.
I have been a drummer for over 33 years and I have purchased many cheap drum sets over the years and have been very pleased with the sound quality (after some tuning and a few additions). Most of these were not what would be considered Top name brands such as Tama, Ludwig, Pearl, Yamaha, etc... , although; sometimes you can also find cheap drum sets from these brands as well. You just need to be patient and decide what your true needs are.
You can see many examples of this at http://www.buycheapdrumsets.com/