In Cork we ate at a pub, and I think it was 11 euros per person for our food. In Dublin we also ate in pubs and in the department store restaurants, I think it was Marks and Spencers and we had a great rooftop view of the city.
If you're working on a budget, try to eat a hearty breakfast and a late lunch so you can take advantage of the lunch prices. I noticed that they loved their potatoes, so I'd fill up and use those carbs walking around. Some places have huge portions so you can share a larger dish, while the other person orders a smaller side, like soup, salad or appetizer.
You also can do as the locals do, and get food at the market and make your own picnic, sandwiches, snacks, etc which can keep you full so you don't overindulge at the restaurant.