407 SW HDI FAP 135 – 180 € for additives refill?

Hello My wife brought our 407 sw HDI FAP 135 to the workshop today, because the message “additive level came low”. Now she came back and said that it should cost 180 €. Sorry, but do they want to fuck us? 180 € for refilling additives? Is there gold in it dissolved or what? Does that cost so much? Thanks for information Jürgen