I've noticed certain differences that seem unnecessary in pricing of plane tickets. Like most of the tickets you'd buy leaving DR are more experensive that those going in, regardless of the fact that the same distance is being travelled.

About general prices being a foreigner, if something doesn't have a price tag then the likelihood is that once the seller notices you are a foreigner they will try to increase the price.

Going to any place you don't know the rules of can be expensive in many ways.