Depends...
xSpAnIaRdx
Almost invariably it costs a foreigner from a wealthier country more to live here than it costs a Dominican. Why?
1. You have to pay for a visa, residency, etc.
2. You may have taxes from your home country that you have to figure into the equation; they aren't a Dominican cost, but they are part of your normal living expenses.
3. People tend to charge you more for things you buy, and services they provide, than they would charge a local person.
4.While many people here either get insurance through their work or on their own, most don't have insurance, or at least not on the level you would like it. Then there is car insurance as well.
5. You probably aren't going to take public transportation. Instead you will buy a car, and those are expensive here, with high gas prices as well.
6. You probably will want to make trips back to your home country. Travel isn't cheap.
7. This is an island. Almost everything is imported (and taxed). So when you buy a TV or a computer, or an appliance, it is probably going to cost you double or triple what you are used to paying for it in your home country.
8. I should add, it can actually be much more dangerous for you to live using public transportation and in a lower class area, because of the perception people have (like burglars & muggers) that you, as a foreigner are made of euros or dollars. A Dominican doesn't have this impediment.
So yes, the Dominicans you know may very well live on much less than people are telling you, but will you be able to? Most people cannot.
All in all, you are used to a higher standard of living. You require better quality in your possessions, your clothes--just about everything, and that costs. Things you see as essential are considered luxuries by those you are comparing cost of living with. You may not notice that on a visit.
It is very stressful to try to live at even the lower middle-class level here. There are foreigners (from developed countries) that manage to do it, but they are the exceptions, not the norm. What you call "middle class" in your home country is probably considered "rich" by the typical middle class Dominican.
Having said all this, it does obviously depend on your lifestyle and how many mouths you have to feed. You can, indeed, live on less than $3000 a month, if you are willing to make some sacrifices, and don't live in the high priced areas. My rent is only 7,500 for a three BR two bath apt, but I have to put up with a dirt road, noisy neighbors, and many other inconveniences which I wouldn't have if I were living in the more elite areas of the city.