The best business lunch value I have found in Santo Domingo, is inside Mega Centro in Santo Domingo East, located at the corner of Ave. San Vicente and Ave Mella. I don't know the name of the place, but you enter the mall through the primary entance that faces this intersection (during the week, at lunchtime, there are usually lots of empty spaces right out in front).
Enter the front, go up the escalator to the second floor, and the restaurant is on the right side at the top (the place may be called GameWorks). As you enter, they have a ton of kids gaming machines on the right, and a sports bar on the left.
You can get a large, healthy sandwich, french fries, unlimited soft drinks, and an ice cream for dessert, all for about RD$165. They also give you a one hour coupon for free games for your kids for the weekend.
The best thing to me is that it is quiet enough to hold a business conversation, the waitresses attend you promptly, and you can actually get in and out in about 45 minutes.
(and while this may be a good idea of a business lunch for a business OWNER, it may not be for some manager/employee who is on an expense account and expects a $3000 bottle of wine and lots of fawning by the help, as he enjoys his 3 hour lunch)