I could have used the raw statistics but it would have undermined the whole point. People don't make fully rational decisions - even when up/down voting.
But to get analytical, the argument is not that you buy everything that is advertised. The argument is that your purchases are primarily based upon how the purchase makes you feel. Even for everyday "necessities" like toilet paper which Japan gets away just fine without (they use bidet style toilets which are more effective at cleaning). In North America a bidet "feels" weird so nobody has one. When you get down to it toilet paper is not a logical purchase at all - better alternatives exist.
Further the argument is not that people don't have free will, quite the contrary. The argument is that the decision process is based upon considerations outside the efficacy of the product. Consumers don't do scientific studies on the products they buy, they only infer based upon heuristics which are primarily emotional in nature. This is why people consider bad tasting medecine to be more effective, and why Buckley's uses the slogan, "Tastes terrible, but works!".