Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Works but not worth the $$

I purchased P21S for my BMW's alloy wheels after reading a positive review on the BMW forums. BMW's are known for generating huge amounts of black brake dust & grime which are difficult to remove. P21S did work, but no better than far less expensive wheel cleaners widely available at any discount store. I got basically the same results from using Simple Green, which you can buy in a gallon jug at the warehouse clubs for about $8.