Personally I'm thinking about setting the price to create a card high and static. Something like 1 HBD per card. Because creating cards generates the governance token and copying cards does not, I think I can get away with this.

I honestly think it might be a really bad idea to allow the governance token to affect the price of card ownership, because the oligarchy formed could choose to lower the price and then jack it up later and lock everyone else out after they scoop up a ton of cheap cards.

won't it be great if the original creator earn some royalties from subsequent copies?

You might be misunderstanding me. No one can create a copy from a copy. All "proxy cards" (copies) can only be created by paying the owner of the original. I wouldn't want the price to go up because then players would get priced out of copying the most popular cards. Interesting idea though.