Why is there such a large price difference between the A350 and B787? What are the reasons for quite significant difference in price between the Airbus A350 and Boeing 787? List prices for the A350-900 and 787-9 are around 317 million USD and 190 million USD respectively.
Those prices are not the actual prices airlines pay for those planes. They get big discounts and more complex contractual terms. It's not like buying a box of pasta.
In conclusion, you can't assume that the price difference means a different cost of the components for the manufacturer