Instead of having, "Add an extra Kingdom Action card costing exactly $5 to the Secret Society deck," why not have 'move an Action card from the Supply costing
to the Secret Society deck?"
This avoids the problem of rules lawyers trying to dig for a Knight or Small Castle, or of people trying to move a card from the Trash or elsewhere, and avoids the use of "Kingdom" in a card text, which DXV found to be unhelpful when playtesting Empires.
Also, you can rephrase "Before the game" to "Setup:"
Also, I don't think you need "exactly
"--you can just say
.
Finally, cost-reducers can put more expensive cards into the SS deck. Is that your intent? Or were you trying to get around that with "exactly"?