Since I just nabbed the last girl from Karole, I figured I have no reason to fight Karole anymore, and would benefit more from spending my Combativity on Fredy.

Why? Well:
-beating Fredy rewards 29.5k money
-beating Karole rewards 1 out of 16 presents.
-out of Karole's 16 presents, only 5 value higher than 29.5k money. And while I don't know whether the chance to get Karole's rewards are spread evenly, in my experience so far, the common rewards are indeed way more common than the epic or legendary rewards, bringing the avarage value I gained so far from them way below aforementioned 29.5k

Suggestion for a simple fix: add a flat 15k to 20k money to the rewards from fighting Karole. The cheapest present + such a flat fee would still be way below the 29.5k from Fredy, but the avarage gain would be much closer to it, and probably even slightly above it.