Sales order price vs Invoice price - Difference mitigation

Dear Gurus,

I am dealing with a situation on my project. Please refer to below screen shots.

1. Sales order was created in Jan 2021. Sales order Price is calculated cost (EK02) standard price from material master (Accounting 1) + Mark up = 5033.05

2. Part is manufactured in the month of Aug 2021

3. Before delivery in the meantime, part material standard price is changed in Aug 2021 = USD 3875.33

4. Delivery is created after material master standard price is changed. So delivery accounting document is picking up latest new standard material master price.

5. Invoice is created. So it is also picking up new price. That is USD 3875.33 + Mark up = USD 6781.83

Since business already committed Sales order price to customer, we need to stick to the same price (Jan 2021 month price) and not new changed price in material master.

Gurus how we can achieve this in a standard way. I am also showing here the current VTLA screen shot below

Could we achieve this by changing routine with other standard one (which one?) OR do we need to develop a new routine.

Kindly help with your inputs/suggestions.

Regards

Vishwas