There was a faint pop as a gaudy sphere flared into existence and rolled down to meet a basket of other sparkling spheres. The shopkeeper made a mental note of it without turning or pausing his conversation.
"Now this promise is especially exquisite. Large, smooth, simple. You don't see many of these. See how rich the pink centre is? This promise came straight from the heart, with straight-forward simple words and intentions."
He paused, seeing that slight shift in weight the customer made when disinterest kicked in.
"But simple is not for everyone." He picked up another sphere instead. "Here's a pretty thing. Not perfectly round, I know. That slight distortion comes from the person being drunk. See the scrolling loops linked up the side? One loop for every "never" they told themselves. The linking comes from the "nevers" being said so close together. And this blue! You don't get blue that deep unless the person has been sad a long time. A touch of despair setting in too, judging by the smoky black rim."
Another sphere popped into existence behind him, the customer's eyes drawing towards it with a slight curious frown. He turned, observing the new sphere. It was dull, pink and black, small and plain. He gathered it up and held it out for the customer to take. The customer lifted it up to the light, then back down and rolled it in her palms. She asked for its story.
"Ah! This person doesn't believe they will be able to keep their promise, but intends to try anyway. The size in this case comes from few words spoken, most likely they said "ok" to someone else stating the promise terms. They must love the person, that's where the pink comes from, of course, and the black is opaque because the person doesn't see a way out of their despair. Would you like it wrapped to go?"
As the transaction completed, another faint pop sounded, this time followed by a tinkle of broken glass. He winced slightly, then smiled as he waved the customer out of the door. The smile dropped into a sigh as he turned around and reached for the broom. Damn those hollow spheres, empty promises were so easily broken.