I don't know, it seems like a pretty fair deal, considering they setup the systems, the marketing, the base models, and the consumer base for you. They built the game after all.
yeah, I'm not that upset at the 75/25%, but... it gets tough when you consider two things. 1) Sony gives 40+% for PlayerStudio, and 2) when you do anything with organizations they like to get at LEAST 50%. When a lot of times it's the items that sell it.
a solution to this would be to assign the default values to each part (ticket, item), and break up the revenue based on that. Also, always make sure the ticket is sold standalone for those that don't want the items.
In addition to that, you'd figure Valve wants to grow esports and Dota so they could at least maybe change the 75/25 split to something like 70/20/10 (valve/creator/org) to encourage that stuff. but naw, who knows what they're thinking, heh.