I think it's the "who gets harmed along the way" part that makes this a grey area. Is anyone really hurt by having these events? If someone wants to pay $150 for 3 hours at MK more power to them. Same as paying $200 for the HM box thing. I might not think its a great way to spend my money, but it's a free country.
"who gets harmed..." I understand what you are saying. I would say that regular day guests could be harmed. Instead of the park being open to midnight, the park closes and hour earlier to accommodate the 3 hour event. Some might argue it is only an hour, but I would counter that at the end of a regulary scheduled evening that last hour from 11 to 12 can really be a great time to get on rides.
By closing an hour earlier there are more people in the park. plus the additional special event guests. For us that end of evening time really can have impact.