It's called a "voluntary" contribution, Mon, but the letters say unless enough people pay the trip won't happen; also that if you are really strapped you can ask for help but, you know...
DS1 recently had an 8-day trip to the US for £800, including flying to NY and back from Washington, and 3* hotel accommodation plus loads of organised excursions, which was excellent value.
DS2 wanted to go on a 4-day/3-night soccer trip to Spain for well over £500 - said no. I think this Lion King trip is worse value than that.