question about purchase price for marketpress

Hi, I am confused. I purchased the MarketPress eCommerce because on the landing page it claimed "Marketpress has all the features you need (and we’re adding new ones all the time) for one simple, low price.", which I saw to be just "19.00". But as I was checking out, I noticed something (after I accepted the charge) saying that it was a MONTHLY charge of $19.00. Can someone please explain? I am not interested in a recurring charge and only wanted to purchase the plugin itself. Is this possible? Thanks, Melissa Stafford - melissastafford@gmail.com