The Italians have been caught selling rancid and impure olive oil in Australia about once per year (ie. just about every time it's checked). It applied to cheaper and expensive oils, so cost wasn't a judge.

I don't buy Italian olive oils any more because of the wide-spread deception. To be fair to the Italians, they were as dishonest as the Greeks and the Spanish. The list of brands was very long and the levels of rancidity/impurity were worrying.

The only name I remember that was found to be honest was Cobham. I think they're an Australian family business (but could be wrong). I have no affiliation with Cobham in any way, except I buy their extra virgin olive oil.

Interestingly, I know rancid oils are very poisonous, but have never found a reference to the ill effects of rancid oils.