What makes a rookie card valuable?

Related questions

1. What is Nolan Ryan rookie card worth?
2. Has anyone died in the NHL?
3. What is the value of Mario Lemieux rookie card?
4. Is Gretzky the best hockey player?
5. What year was Wayne Gretzky rookie card?
6. How many penalties did Gretzky get?
7. What is the most expensive hockey card in the world?
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10. Are hockey cards worth anything anymore?

Tags

1. #after
2. #athlete
3. #appearances
4. #highest
5. #feature
6. #first
7. #trading
8. #sport
9. #issues
10. #subsequent
11. #within
12. #these
13. #rookie
14. #value
15. #level
16. #competition
17. #participated
18. #collectors