Same thing happened to me coming from Dubai to Frankfurt. Pay the fine on the spot (a similar amount) or else. Customs agents are amazingly good at protecting their rackets.

On the other hand, just watched an episode of "Border Control UK" where they caught two people attempting to smuggle several thousands of cigarettes in their suitcases for purposes of resell in the UK, and they were just given a warning and let off with a joke. Customs agents at Frankfurt would need a break to change their pants first