For example, ‘Endless Horde’ makes the map a lot harder. This should be reflected in the reward you receive for completing the map successfully. Specifically for this modifier, I think a 50% increase in the reward is justified, because of how hard it is. The same goes for other map modifiers, which should reward you proportionally to how makes they make the mission harder.
In addition, conditions that make the map easier, like ‘Less Hordes’ should give you a slightly lowered reward. This would help people climb up the difficulty ladder more gradually, while not incentivizing more skilled take players to take an ‘easy win’ which would be a more boring way to play.