Any pub/cafe carvery will surely have the above for E15. Sinnots, Dicey's, Russell Court, Ripley Court, Cafe Kylemore, O'Neills on Suffolk Street etc. Next year Weatherspoons will be on that list.
There ain't nothing cheap about eating out in Dublin. It does depend on the time of day which you have not specified. If at lunch time then I highly recommend Diceys on Harcourt Street, you won't get lunch cheaper and they may have Turkey & ham on the menu
If you are looking for 'proper' restaurant, you could try La Cave... they have a 2-course early bird christmas menu for 21e with turkey and ham as one of the mains.
Only an occasional visitor to the capital. I got a single course meal in the pub on the opposite site of the river from the Four Courts for €10 including a pint of Guinness.
I didn't think of that. Well they should negotiate a price. Normally if you have a bunch of people you could for example negotiate a free drink or dessert.
It would be helpful if we had some context. But poster does seem desperate.
I'd do lovely turkey sandwiches and some kind of cake in the pub. And still make a profit if it's a tenner a head. Pubs will let you do that if you're bringing a bunch of people in to party. I can't imagine an office party in Dunnes 'restaurant's'. I'd rather stay at home.