I've never had anyone ask us to pay. The part of World Drive that is northeast of the parking plaza does not allow you to enter the MK parking lot, so there is no reason why you would have to pay to do so.
When you go through the MK parking plaza you'll need to stay in the second-to-farthest-right lane (the last one is buses only), and tell the attendant that you are headed to the Poly. You will need to bear right (but NOT turn right) as you leave the booth. Proceed to the stoplight and make a left on Seven Seas Drive.
You do head for the Poly, but you turn off before you get there. Once you are on Seven Seas, look for a sign on the right marking the Guest Drop-off area.