Maybe, but you already pay Mixcloud a £9 fee to earn money, then they take another fee again from the fans pledge. It might be expensive to run, but they're taking a double payment, when they wouldn't have any money coming in at all if there were no creators.
I do agree charging a creator a fee to use the platform up front, then taxing them per tip and subscriber 40% doesn't feel fair. You already getting the membership fee from the creator, why tax there tips. Thats like a waiter paying to work at a restaurant, and not only he has to pay to work there, he also has to split his tips with restaurant, the cook, the busser, and the host And he keeps whats left. Definitely feels like a scam but I'm sure it's because they know, there aren't any other platforms who can do what they do. Give you a website and platform to distribute your content anywhere without worrying bout any infringement so you pretty much pay to play.