Yeah, I get those pretty much every month, as I'm always selling stuff on the 'bay.
As the message says, they'll be taking the money off you (via Paypal) within 10 days of the message. You must have agreed to it in the past, or they couldn't do it.
Ebay selling fees are approaching 10% for some items these days, so that seems like a pretty minimal bill to me. What value of stuff have you sold on ebay within that time period ?