Why is there a higher fee for re-used receiving addresses?
When you have an address with multiple inputs (you have sent bitcoin to the same address multiple times) and you want to send all of those bitcoins to another address, all of those inputs must be included in the transaction, and recording each input takes up space. If you have only sent bitcoin to an address once, it only has one input, therefore the transaction only needs to contain one input, which takes up less space.