For Ukraine this always has been a fight for survival. Anything that results with Ukraine resotring the border to what it was prior to the invasion can be considered a win. Double so if Ukraine regains control over Crimea. And tripple so if Russia loses its ability to launch another invasion. But these are just bonus objectives, it isn't the goal of the war for Ukraine, even if some rethoric makes it seem that way.

The alternative to winning was always ceasing to exist. It might not have happened after this invasion but would have been inevitable. The cost of rebuilding doesn't matter considering the alternative. And I don't see the West abandoning Ukraine in their rebuilding efforts. The EU is almost certainly going to open conversaitions about Ukraine becoming a member. It would probably include a multi year plan of rebuilding with restricted membership before becoming a full member.

And there are tons of people waiting to swoop into Ukraine and buy up the cheap land and develope it. They aren't going to do it out of the good of their hearts but it will still speed up the rebuilding of Ukraine.