No.
It's an option and they keep the money on the basis that they did the job you paid for by posting that there is a Reserve and making sure the item does not sell accidentally for less than the reserve.
But you can save the money and increase the number of bidders by setting you asking price at the lowest price you can comfortably allow it to sell.
Which is to say, you can list free at the Reserve price.
Many buyers ignore auctions with reserves as being too complicated and vaguely dishonest.
