I meant to post this earlier -- sorry for the delay. Thanks to Nancy Reyes for putting together the tasting and tallying the results. So, here they are:
1st place (Sample A): Columela. From Spain, price: $$
2nd place (Sample B): Zatis. From Turkey, price: $
3rd place (Sample C): Napa Valley Naturals. From California, price: $$
4th place (Sample D): Badia a Coltibuono. From Italy, price: $$$
Of those who guessed countries, one person guessed two correctly; three people guessed one country.