Fox Float CTD Evolution vs Fox Float CTD Performance
What's actually increasing the cost in performance fork is it's construction qualitiy. It's slightly better in terms of durability and a bit lighter. Depending on the year of make, performance may also include a new technology or system that the evolution (which is the basic lineup) won't have (thus making it more expensive). Think fox's lineup as this:

evolution -> sunday family ride

performance -> more intense riding

factory -> pro riding