Still waiting on a valuable contribution from the only active Dominican Republic bartender/bar manager/bar-back within this forum to add his in-house professional opinion to the thread. He probably has the best answer.
I'm not as active as I used to be but I'm a bar owner in Santiago.. Beer costs and margins are actually really interesting. Our bar only sells small presidentes (pequeñas) for 125 pesos with tax included, our cost is 53 pesos because of some specials that they offer based on volume. On Thursdays, we sell them for 60 pesos with tax included and it becomes a loss leader (considering ITBIS, overhead etc). The reason why the prices are interesting to me is that the large bottle Presidentes (Grande, not jumbo) only cost 58 pesos vs 53 pesos for the small, and have like 30% more beer inside. This indicates that the actual cost of the liquid inside is only a very small part of the cost of a beer. Cans of beer are also more expensive than bottles and have the same amount of liquid. Cans are 75 pesos from the distributor I believe. As someone already stated, I'd assume 80% of the cost of a beer is bottling, advertising, and distribution.
Another interesting off the topic thing that happens sometimes, we have received presidente bottles with stella artois caps, with stella artois inside instead of presidente.. which indicates that it's all manufactured in the same place!