, have professional ethics, or don't know it, or just entered the business and haven't learned it yet. Another kind is for your important relatives or friends.
5-1%, commodities or high-value or transparent prices.
1-15%, normal.
15-3%, with few black spots, which may be "forced" by customers' low bargaining.
3-5%, which should be classified as semi-robbery.
7%, yes, maybe I don't want to do it, or I really met a rich and stupid customer.
9%, this is not a rebate, but the merchant forgot to collect the money or miscalculated the decimal point.
1%, this is from the merchant, but you need to charge the customer's money. Be careful that it is not for the customer, or it may be for an activity, but it will not be a big commodity.