@graphtar thank you for responding.

Edit: What speaks for the XP is the following (look at the Frost Giants ingame): The 2.70 for 2.03 at lvl 1, 1BCX has a green scale on its card, whereas the 2.04 for 2.04 at lvl 1 has no - as it usually is. Similarly the first sold card (20.35 for a BCX of 1.91) is at max lvl 4 with only 10 cards, whereas later on lvl 4 max cards have both 11 BCX (and those match to the BCX prize). Also there are three cards for sale with 2 BCX, two are the weird ones, which reach lvl 2, the other is the normal one and still at lvl 1. All in-game, Frost Giant. Edit end.
@elindos "Here we can't even zoom on your picture examples." This is just plain nonsense. Use ctrl and + to make everything larger, you can see the pictures then just fine; ctrl and - to make smaller again or ctrl and 0 to get back from anywhere to base 100%.

I have no inclination and no obligation to install discord. Posting this under the most recent post of the official steemmonsters account looks to me just very fine and like a very serious way to approach.

Now to the "more useful" part of the reply. That read like some help.
XP might be the thing. Might be not. I have never heard of this phenomenon/experienced it: "That may also be the reason why sometimes at some levels and card foils, you combine cards and end up at 1/6 or 0/5 instead of 0/6." (With never I mean 0/5 instead of 0/6, it is just normal that at some ranks it starts with 1/x level and on some with 0/x level.)
An alpha card is worth more than a beta card, so it hardly could be a beta card with the additional rest of an alpha card. But whatever, there might be some xp issue. https://steemit.com/steemmonsters/@steemmonsters/kickstarter-update-plans-for-fundition-campaign-and-beta-edition scroll down to "card xp scaling"

If it were an XP issue then indeed it would be only a graphics and description issue. As I said, a nuisance.
If not, it would be more serious, as I wrote. To list a card which is more expensive for cheaper is about real steem money. Although it is easy to see in the Frost Giant 2.03 and 2.70 example, it is not so very easy to see for cards which are combined. Then it would mean you can absolutely not trust the listing but would have to calculate every time if this listed price is accurate to BCX. (See, e.g. the first Frost Giant at 20.35 instead of 19.10. It is also to be noted that the difference here is 1.25, so it is not simply double the difference from 2.03 to 2.70 (67 cents) which would be 1.34 (or including a little variation 1.35).)