I wouldn't compare them to geisha. That has to do with aesthetics and sexuality. The whole purpose of their existence was to be pleasing to others. They might spend their entire lives paying back their debt. Olympians are more comparable to Chinese performers in the past, who also went through grueling training from a young age. Their training was just as physically harsh, they were separated from parents (or abandoned, or simply orphans) and were only respected if they did very well and became famous. Check out the movie Farewell, My Concubine to see what it was like.