Earlier quoted context omitted.
I'm sorry for not been clear enough but you probably misinterpreted that, it's like when someone visit you and brought a bottle of fine wine as present, you welcome him and says "This is so unnecessary! (but of course I appreciate that)", notice the emotion and hands on his face? well maybe this is a cultural thing.
I think the stereotypical English phrase is "Aw, you shouldn't have!"
This comic essentially expresses day to day events with alternate vocabulary, often creating quick and repeated exhaling of air through open mouth or uprising of mouth corners.