That has always been the case for AP labels via ebay, as AP need to be advised of cancellation within the specified time, so they can ensure the label is not used.  Ebay on occassions will give a refund as a matter of  goodwill, which would appear to be the case for you previously.  Personally I dont see any reason for them to make a second goodwill payment, as you should be aware of your responsibility due to previous event.

Ap labels have always been charged at time of generation, not when printed or shipped.