Yes the system is confusing, I had a buyer this week purchase 2 books, they advised me they needed to pick up preferable on Friday for a birthday party on Sunday they purchased Tuesday night and were paying via bank deposit.  They did think that had to pay before hand but did not realise that I had to post, I advised that there was very little chance of Australia Post delivering on Friday as I'm in another state, anyway I rang and told him how it works, he ended up paying via Courier which was still only a 50% chance of getting there in time, we were with the same bank so payment was there on Wed, I sent via Fastway and he received on Friday.