The UC Davis tests took samples from supermarket shelves, which you can say is representative, but if you do your homework and buy good oil from a reliable importer then you can get excellent quality at lower prices than California product for sure. For example the oil from Herdade do Esporão. Your criteria should be, in order - reliable source, age of the oil, and flavor / aroma. Phenols... who knows how and when they were tested.
Generic supermarket oil is almost certainly (1) old (2) not what it is labeled at - you can imagine that if something makes it to the shelf at Whole Foods, for $9/bottle, they bought it for $5/bottle or less, which before importation costs is probably $2/litre bulk oil, mixed together so that the percentage of evoo is just high enough to get acidity levels and other testable parameters to pass lab tests. (my parents, in their retirement, produce olive oil, so you can bet I never hear the end of how cheap fake oil is flooding the market