Thank you for reporting all of these aethernus! I have just found and fixed an issue with how we were getting Cardmarket prices, which should hopefully fix resolve of these problems. It looks like in some cases it was returning outdated prices, which skewed the numbers quite a bit. Most of the cards you listed should now show more accurate prices, and the rest should get updated in the next few days.
MustaKotka: It's whatever Cardmarket shows as the trend price. I believe this is the cheapest across all languages, but I'm not sure.