Recently I've been reading Michael Emmerich's "New Penguin Parallel Text" for Japanese short stories. In Yoshimoto Banana's "A Little Darkness," there's a passage that describes how the narrator's father didn't like planned birthday celebrations (he avoids them and gets dead drunk), to the point where the mother and daughter surprise him with a middle of the night birthday party while he's sleeping, and so in this case he comes home, not drunk, like a nice, regular day. At that point, Yoshimoto writes:
In Emmerich's translation, the passage goes: "It never occurred to us that if we had to go to so much trouble, we might as well not celebrate."
In this thread, a seemingly similar use of
-てまで has a meaning of weighing the worth of one's actions. Is that what is going on here, but the portion "we might as well not celebrate" is merely implied in the Japanese, and made explicit in the translation? If so, how can we reach that conclusion based on this short and seemingly simple phrase?
Is it common to drop that secondary clause? Or is this a sort of stock phrase? I'm having trouble understanding the leap here.
Here's the full passage for context: