These are excellent points. When we shop at the markets (i.e. Hi Lo, L&M, etc), we only buy local items and stay from the imported stuff. I see no reason to buy a $5 bag of Doritos, when I came to Jamaica to experience things that we can't get at home.
Also, items like sunscreen and toiletries are brought from home. Although you can find them on the island, you pay a premium for the imported brands.