Good question Temi, i dont value just directories this way mainly all websites but i tend to go in the order of:
- Backlinks (the more backlinks, the more value)
- Traffic (valuable source of traffic bumps up price)
- Domain Age (i believe this at times v. important)
- Directory Software (directory licence (if any))
- Skin (custom made adds value)
- PageRank (for those finatics out there)