* He's a private person: Robert Pattinson isn't known for public appearances or interacting with fans in that way. He rarely attends fan events or charity dinners.
* No official avenues: There's no official way to "buy" a meal with him. You can't find it on any auction website or through celebrity meet-and-greet services.
* It's purely speculative: The cost would depend on factors like the location, the type of restaurant, the length of the meal, and even the level of privacy requested.
It's highly unlikely that you would ever have the opportunity to have lunch or dinner with Robert Pattinson.
Instead of focusing on the cost, consider enjoying his work as an actor and appreciating him from a distance.