How transfer price on transfer order is calculated

Hello

Would like to understand how transfer price on transfer order is calculated

In our project we have actual (FIFO) costing method and Lot level costing

I have only 2 layers for item, first layer 5 qty $10 and second layer 5 qty at $5

Created a transfer order for 5 qty and transfer price being calculated is $37.50

The order is under same BU and LE so no supply chain financial orchestration rules are not used nor any transfer price rules are involved.

and this order is a manual order created from Inventory management not internal transfer or requisition source.

Anyone can help on how transfer price is being calculated on transfer orders