Oh, I just remembered as I played one of these last week. There are a lot of standalone scenarios which are cheaper. Searching „Arkham Horror Einzelszenario" should reveal these. They cost about 20-30€ each which is expensive for a single scenario but I find that some have a lot of replayability. The three I have played are Karneval des Schreckens, Mord im Excelsior-hotel, and Der Blob, der alles fraß. All are fantastic.
Googling the standalone scenarios, I found a free fan-made cruise ship scenario which is print and play. Unfortunately, it is only available in English. Perhaps if printing is an option for you, you could find some scenarios this way.
Edit: I did the googling and found pages dedicated to fan made scenarios here and here.
I learned all too quickly to never go all in on Isengard attacking Rohan. Despite all laws of probability, my opponent has a 100% chance of having both ent cards and a companion near Fangorn forest.