My wife has always told me thesame thing. U get the gringo prices, let me negociate...... After a couple of years in the campo, I now go local shopping for chicken, cigarettes, etc.....( zhe rest is home grown). Im blond and blue eyed, speak dominican as if had a seizure( eventhough people actually comment on how fluent I ve become). The trick is to never over pay, if u think they are charging too much tell them as much, once. On thesecond occasion never buy anything again( its happened to me for 15 pesos on a pack of marlborough cigarrettes), theword spreadaround, leople making fun of the vendor, bar time story....... U aquire a reputation of no **** taken, so nobody tries a stunt again.
Out of ure campo, its more complicated to know if they are overcharging. I always run around on a motoconcho in big cities, leave the pickup at supemarket, andthey are real helpful in that case( because they want a tip). And if u need a specific, rare piece of equipment ( like a samsung galaxy 10.1 charger) and dont have time to wait foramazon to deliever, send the motoconcho alone......