Ukraine spent less time attacking into Kursk than Russia spent taking it back, so logically speaking Russia was on the offensive for longer. Ukraine took what it took in weeks, Russia fought to take it back for months.
Considering that you lose more on the offensive than on the defensive, I believe that it reasonable to expect that on net Ukraine won from that adventure.
That's not to say that the opportunity cost was worth it, but it's hardly a disaster.
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