Here’s a link to a consumer review org that actually tested it with standardized loads and measured drying times. They don’t work, takes just as long and cost the same in electricity.

https://www.choice.com.au/home-and-living/laundry-and-cleaning/dryers/articles/dryer-ball-review

It’s sad that nowadays most “reviews” are just going by feelz and not by numbers. The placebo is strong with this category.