Wether or not you consider it a sacrifice is really a question of frame of reference. I don't think there's any objective truth in it being a sacrifice or not.
However, given that the person I responded to want to have kids, I assumed that having kids was important to them.
And given that getting kids is basically something that you devote the rest of your life to it comes in the ball park of "as important to you as your life" if you choose to have them.
Good point, sacrifice certainly has some subjectivity to it. If someone uses the term “ultimate sacrifice” then they are ranking sacrifices and have some rationale.
I don’t think there’s an objective arbiter, but for terms of communication there is some need for subjective consensus. I might view chewing sugarless gum as the “ultimate sacrifice” but many others will not.
I don’t think that choosing not to have kids is the ultimate or greatest sacrifice and I gave some of my reasoning. Perhaps if someone thinks kids are the sole purpose in life then giving that up would the ultimate, but I don’t know if that’s very common. And if so, would be quite sad as such a sacrifice for the sake of climate change would be so inconsequential and a waste (like ending one’s own life to prevent emitting carbon from breathing).
However, given that the person I responded to want to have kids, I assumed that having kids was important to them.
And given that getting kids is basically something that you devote the rest of your life to it comes in the ball park of "as important to you as your life" if you choose to have them.
So to them, it ought to be an ultimate sacrifice.