To pay, or not to pay
In this particular case, design and style have definitely trumped usefulness. Here the designer obviously looked at all the words, and the shape of the arrow and decided that bottom to top was what would look prettiest.
However, if you’re like me, you’ve already read it from top to bottom, and been very very confused about this shop’s attitude toward shoplifting. “Before you leave forget to pay, Do Not STOP!!!” Hmmm… slightly mixed message.