When I click on a date on that website, e.g. 16.01. I see tickets for 69.90€ on the coach wagon from Berlin to Paris.

When you said night train you can sleep on I assumed sleeper cars. But to be fair, I always looked at trains to/from Vienna, maybe that's the exception in prices.

Coach is a sleeper car, you just share the cabin with up to 5 people on bunk beds. Although on newer carriages (which I think is the one that goes to Paris) those are sleeping capsules where you have more privacy.

I took the trip to Vienna in one of the old bunk bed cars for 60€ and it was fine. I liked the experience of chatting with the fellow passengers in the cabin that you usually don’t have on a normal train ride.