To go along with what Julie has already said (and I totally agree with), take a look at the sample menus online to see what you might like to order. That will give you a good idea of the possible cash cost.
For example, DH and I love Jiko but chose not to use 2TS credits for it during our last trip. This is mostly because we don't usually order entrees here because we love the starters and appetizers -- end up ordering soup, salad, taste of africa, lentil pastilla and the flatbread. It wouldn't be worth the table credits for us!