This is how the order system works.
You get money step by step while the order is being delivered. Every time a truck leaves your storage with items, a small part of the payment is added to your money.

When the order is fully done, you get Biz Points, not extra cash at the end, because the money has already been added during the delivery.

If the numbers look the same, it can be because the money counter rounds small changes.

This is the normal way the game gives out money for orders.