Most Dominican places are very stingy with their coffee, especially considering how relatively cheap it is here. You're lucky to get a 5oz-6oz cup at best. I was at a Santo Domingo Coffee kiosk is Las Galerias Mall in SD about 4 years ago and paid almost $2.50 for a dinky cup of coffee.
I'm paying 10 pesos for a communion cup of coffee when I do buy out, which is rare. They put waaaaaaaay too much sugar in it for me.