I used to think the same and then read about a study that lab tested a bunch of brands. The most expensive ones were more likely to be adulterated. It makes sen

I used to think the same and then read about a study that lab tested a bunch of brands. The most expensive ones were more likely to be adulterated. It makes sense in a way. They command the highest margin, ie, highest reward for adulteration. That said this was in a common US grocery store. It may not apply to really high end artesenal type olive oil generally bought by people who it wouldn't be worth to adulterate. Also, it's worth noting that there a lot of places along the supply chain where things can be adulterated, and the incentives aren't all the same for every actor along the chain.