Do you have a source where a dev confirms that fast travel doesn't cost any money?
Otherwise, at this point in time, all we have to go on for this particular detail is this German article.
It may be possible that the journalist Stephen Freundorfer might be compeletely wrong, perhaps we wrote incorrect information based on having heard about the carriage travel system, maybe he never used the fast travel system and was just guessing that there was a fee involved.
However, as for the translation, it seems pretty clear that Mr. Freundorfer claims there is some sort of fee charged for using fast travel. It's a very short word, "kostenpflichtig"