Most retailers can have more than 100 % mark up ,and when they have massive 50 % off sales ,people get all excited
Many retailers I deal with work on a minimum of 100 %,some even as high as 150 %,then throw in GST
Buying power,volumes,regular customer can get bigger ,better deals than 1 off customers
Ill sell a $600 item to a new customer, but a regular customer mite be paying $500 ....