My stratergy is running a route at default prices if possible.
When entering a market where there already is someone flying I keep default price even if the competitor has higher price. If competitor then matches I stay still.
If competitor reduces prices below mine I try to match price, but not go lower then the lowest price offered.
I have routes in this world where neither me or opponent has changed prices, and we fly with the marketshare we have gained. In other routes the competition keeps lowering price, and I will try to follow to prevent losing money. I am pretty sure I have not been the first to lower the price below competiton except when entering a market where the price is higher then my default price.