I don't know whether the pricing is reasonable. It sounds to me like it's more than what would be necessary to cover costs (is it more than an hour of administrative work?), so Disney will probably be earning some money with this. This wouldn't be problematic by itself (they are a business, after all), but because they are imposing this on third parties unilaterally, it seems questionable. I'd feel better about this if this fee were mentioned in the existing contracts.
Even if we agree with the fee being necessary, I certainly disagree with the way they are rolling this out. From my perspective, they should have announced this with several months' notice. Then the market would have had time to adjust and price this in. It's hard to see a reason why Disney would have had to roll this out with less than a month until it goes live.