The value of Greek slaves was more tied to skill than ethnicity. Greek culture valued education and Greek children were more likely to be brought up to read and write and to understand logic and argumentation. Skilled slaves were pretty much always more valuable and literacy was a highly valued skill. We have evidence that Cato, for example, had his slaves buy and educate children for a year in order to resell them at a higher price. In the later empire, literate slaves become immensely powerful because slaves were considered ideal for the work of bureaucrats for two reasons. Firstly, because aristocrats were expected to get money from land ownership and not from labor and secondly, because slaves could legally have no family of their own and were therefore considered less susceptible to corruption. Literacy wasn't the only valued skill though. Talented cooks, for example, were often times the most expensive slaves on the market.

Exotic or unusual looking slaves could also fetch a higher price at a market and were often used as kind of "display pieces." (I'm sorry for all the scare quotes, but I want to be very clear that these are not my personal opinions.) There is a Hellenistic bronze at the Met which seems to show one such slave. Probably the piece originally showed him carrying something for his master. Literary accounts tell us that slaves whose appearances stood out where frequently used as servers or entertainers at banquets. This included slaves that are designated in our texts as "Ethiopian" or a "flower of Asia" we also have later accounts describing blonde-haired, blue-eyed slaves being sold for their unusual appearance. Often these "exotic" slaves were also chosen for being young, strong, healthy, and otherwise sexually desirable. On the complete other end of the scale, some of these "display" slaves are considered grotesque and are dwarves or hunchbacks or otherwise "entertaining" in their physical oddity.