There are lots of cheap rock tumblers on the market. None of them will compare with the two major brands, Thumler's and Lortone. When you buy a Thumler's Rock Tumbler or a Lortone Rock Tumbler you are buying a tumbler that is made to last for many years. It is not uncommon to see one of these tumblers that is 20 years old and still working.
Thumler's and Lortone rock tumblers are made of high quality parts and thick rubber barrels. This makes for QUIET rock polishing.
I looked at the rock tumbler a major discount retailer sells. It comes with a 2 WEEK warranty. The rock polishing process takes 4 weeks to complete, so this tumbler is not meant to do anything except frustrate the owner (or purchaser). If you are getting one of these rock tumblers for a child (of any age), you are setting them up for failure! They will never know if they like rock tumbling when they have a tumbler that is not meant to finish the job.
Any tumbler with a plastic barrel is noisy. We are talking the type of noise that makes you cover your ears.
Plastic barrels will NOT tumble rough stones. You must use pre-tumbled stones so you won't wear a hole in the plastic barrel.
Another common "toy" rock tumbler looks very similar to a Lortone rock tumbler. It appears that the company that makes them sent one of Lortone's tumblers to China and said make this as cheap as possible.
I have never heard of one of these rock tumblers lasting for more that a couple of weeks. Most don't last more that a few hours! The belts break within hours, and if you keep replacing them or if you replace them with a quality belt, then the pulleys break. Once again, you are setting yourself up for a huge disappointment with one of these "toys."
Thumler's and Lortone rock tumblers cost more up front, but in the long run you get a lifetime hobby. Being able to polish almost any rock in a quiet, long lasting rock tumbler is a satisfying experience.