Sale of same Item with different MRP in the same store

Based on the information in the erpnext documentation…
https://erpnext.org/docs/user/manual/en/stock/item/item-valuation-fifo-and-moving-average

If we use FIFO, ERPNext will reduce the quantity of the Item priced at X first and then Y. Our query is how will that effect the price of items. For example, when we have item X with the following scenario how is the price not changing during the sale

First buy… Item X - Qty 2 - Price 20.00
Next buy… Item X - Qty 5 - Price 30.00

When we have a sale of Item X - Qty 4, technically we should have…
Item X - Qty 2 - Price 20.00
Item X - Qty 2 - Price 30.00
Total Price… 100.00

but now we get Item X - Qty 4- Price 20.00 = Total Price 80.00

Can you advice how to achieve this scenario, or can we achieve this in erpnext.

Any possible option to get this done in Frappe Store module?