Possible Clues:

• On which one might rank the best skaters?
• Variable amounts of trombone practice?
• Fee structure used by some therapists
• More and more bread on this slippery bit of fish?
• Streaming something for musicians with flexible price structure
• Variable pay schedule
• Wages going up sounds like they are going down pecking order
• Flexible fee system
• What to use to calculate climb after slipping?
• Means of varying pay etc in relation to other factors