Why do you use rituals to avoid 500?

Because 50 is a curse abroad and unlucky at home, you can't surpass 50 yuan, but you can't be lower than 50 yuan, usually 30 yuan or 40 yuan, and you can't surpass 20 yuan, so no one will scold you. Being lower than 20 yuan is swearing, which will be looked down upon and unlucky.