https://airwaysmag.com/best-of-airways/737max-vs-a320neo/

“Although the 737-800 (and -8 MAX) have a nominal advantage in operating costs over the A320ceo/neo, Airbus has a (not-so) secret weapon up its sleeve that has more than evened the playing field: inertia in airline fleet planning. When an airline already has a large fleet of a certain type of aircraft, it is very likely to place replacement or growth orders for that same type—due to the cost savings offered by the commonality of all the divisions of the type.

Thus, the majority of carriers have ported over from the NG to the MAX and from the ceo to the neo. At the same time, Airbus has practiced aggressive salesmanship, especially in offering special deals on the A320 to startup airlines, particularly LCCs, which had traditionally been ignored by both manufacturers. Sometimes, the strategy failed, but just as frequently, it generated tangible success and growth”

I wonder how they get “aggressive salesmanship”

Subsidies allows Airbus to undercut especially in the LCC world.