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I didn't check them all, but the first one is being offered to me as a 3.37 Euro Kindle edition here. I guess something about your country settings or the location of the Amazon website you use doesn't line up.
Beans: Thalia, Amazon
Le petit prince: Thalia, Amazon
Same with the other two. They are available in Germany, but not for you :P
Jokes aside: Contact Amazon/Google support (I guess you might need to change country settings? No idea.) or buy them from a German shop like thalia.de, ebook.de, hugendubel.de or your local bookstore.