Sins Rebellion, with a massive 15 card-set, costs ~5 euro cents per card.
On the other end of the scale, Casey's Revenge of the Titans is a 5 card-set that costs ~16 cents per card.
The Bridge is a 6-card set, and yields around ~12 cents.
The equilibrium price for an entire set after the IPO is thus in the vicinity of 75 cents, assuming that a sufficient number of people want to collect it. This is stabilised by a fixed value of the badge at 100XP. I pegged this estimate of 75 cents ballpark from the total number of games that I own with trading cards.
As a secondary effect, for games like Skulls of the Shogun, the set price is more like 55 cents. It's highly likely, judging by the game itself, that few people want to collect the set. At the opposite end of the spectrum, Path of Exile commands an absurdly high price for its sets. Both are low circulation sets with high imbalance of sellers and buyers, I should modify the last post by saying "the number and kind of owners, and their response to the game".