I really recommend to take the night train for the return trip.
Also better than paying 300 EUR or more for a hotel room is to travel by bus which starts the return trip 1 hour after the show. SO you can sleep in the bus.
Another option: Check hotels in VRR (Verkehrsverbund Rhein-Ruhr). Because the ESC ticket can be used till 3:00 a.m. of 15.05. you can also book a night accomodation 20 or 30 km in the near of Dusseldorf. Then you have to check S-Bahn connections at this time.
You could also rent a caravan for four or more people. Maybe it saves a lot of money.
The suggestion with esc-privatrooms was still given.
But if you enter "Monteurwohnung Düsseldorf" at Google or check some small ads websites for this you
can also find some offers (maybe now it is too late for this option).
There are a lot of possibilities how you can avoid to rent a night room for high prices.
It's often a question of creativity to find out other and unconventional solutions.
The best way is to start return trip after the show where you can sleep in the bus.
