As you mention, it gets even screwier given the opportunity to put a "nicht" (not) at the very end of a sentence to lead listeners down a garden path.
In German, the word order "I believe you not" is the proper way to phrase that sentiment, without being pithy about it.
As you mention, it gets even screwier given the opportunity to put a "nicht" (not) at the very end of a sentence to lead listeners down a garden path.