Export and Trade Buyer Credit and line of Credit pricing

I am interested to develop a pricing tool for international bank line of credit to facilitate the request of buyers to purchases export from Saudi Arabia. I am looking to build the pricing tool taking in consideration the full equation of the price (cost of capital+ Cost of operation+ Cost of Fund+ Risk Premium- Adjustment for preferential rate).

We need to know the benchmark for the tool and how we can identify the value of Adjustment for preferential rate without affecting the financial sustainability of the local bank in Saudi Arabia