Is Apple charging for free apps in the Mac Store?

I signed up for the app store last week and downloaded a free app, but have now seen a charge of 1.98 euro (or equivalent of US$2.50) on my credit card account. There was no email, invoice or anything from Apple and no indication of a purchase from Apple in my mac store account. Could this be an authorization hold? Any info on this would be great, we're looking at porting some apps to the store and can only imagine what kind of customer service nightmare this might be.