With a Pro account you are able to configure the price of your photo book and make money each time it gets sold. Open the album and click on the three dots top right to open the menu. Select 'photo book price...' and setup your commission.
The commission compensates for your work as creator of the album. Visitors can select the product, size and shape they prefer and complete their purchase. 100% of your custom fee will be paid out to you within two working days. You'll receive your earnings on the account used to pay your Pro account. There is no minimum payout.