I've noticed that some cards or either overvalued or undervalued. Right now I can only think of two examples: Scabrous Skin and Cautious Sneak. Scabrous Skin is clearly better than Solid Mail Since it has the same armor and triggers more, but is valued under it. Cautious Sneak is obviously worse than Run, but has the same value as Dash. Those are all of the cards I can think of right now, but I think there are more.
Cautious Sneak is valued as copper -, while run is copper and Dash is copper+. So it affects item levels, often in critical ways. Scabruous Skin is a monster card, and not really a cause for concern. End of story.
To add some info to Jade's post if you're not familiar with the details of the grading system, each card quality level (gold, silver, etc) has an assigned value for determining item level/cost, but within a quality level some cards are assigned pluses or minuses making them cost slightly more or less than their counterparts of the same quality while not actually pushing them up or down far enough to enter the next quality level. There is no way to know that by looking at the cards though. You'd have to peruse the actual game's card data.
