> It is about cost/benefit.

This is truer then you know, the world must make the cost of Russia trying to take over another country so expensive both financially and militarily that they do not try this again.

Don't forget Ukraine is not the first, Russia has invaded and sometimes even entirely annexed countries in the past.

> If Ukraine would tell: We are looking for a compromise (no NATO membership, Crimea belongs to Russia, ...), I could change my mind and support them.

Ukraines mere existence is what upsets Russia, it's the reason for this war. It has nothing to do with Crimea and nothing to do with NATO.

Russia wants all of Ukraine, they want to subjugate them completely.