My employer never bothers switching to any competitor because Stripe match any deal that their competitors present to us.
Could you, a single person and $500m of seed funding match Stripe's prices? Not without hemorrhaging cash.
One of Amazon's moats is low pricing as well, which can only be achieved with eye-watering scale (their margins are 0% in some categories, they make it up by delaying payments to vendors and pocketing the interest).