Hi
I am Moamen Mashael, Expert Magento Developer
I am available for next few hrs to customize checkout for your store to depend on product_payed attribute
i understand this
"In the first step the visitor pay the product price only. The user pay only product price, if product_payed status is no.
If the product_payed status is yes the user pay only shipping fee.
In this case you have to exclude the price from cart or set product price to 0,00. The user pay only shipping fee."