Drake Bay has two supermarkets and several smaller ones called pulperias. At the supermarkets you will find a varity of products that are essential and also some which are not essential. One must understand that because of the culture difference you might not find all you want.
Also there is even a little drugstore and fruit shops where you can find fresh vegetables and fruits. Due to our fruits and vegetables do not have to be frozen to move around Costa Rica everything is tasty, since the freezing process diminishes the taste of them.
The prices in Drake are the same for tourists and locals.