Appears to be a pricing error when booking parking at Sydney Airport. If you book an hour via the Sydney Airport website, it'll show as $0.00 for an hour parking for Blu Emu Parking however when you put the time for 2 hours, it'll show the normal price. I have went through the booking process and had a confirmation email sent confirming $0.00 on the invoice however have not used. You do need to enter your credit card number though.
If anyone needs to go to pickup relatives/friends at Sydney Airport and doesn't want to be voluntarily robbed by Sydney Airport Corporation and has time to try this method, let me know if it works!
Even if its free its not worth it, its a pain in the ass to get to n from the AP