Board Game Arena

I don't know if this is the right place. But I am to low level to may speak in the chat
I play a turn based game spyrium. Every time he says you don't have enough money.
But by my name I see: number workers, and then that golden thing with 7 and 2 green crystals. I have 7 money isn't it?
I want now buy a green card with cost 6 in upper right corner. And i have already two buildings, but i thought that the green cards are separate?! And you don't have to pay extra costs.
I discover it is too long ago I play this, but I can't give up. I have first play this again in real time before I understand the game again. :-S

Don't forget that you also have to pay the cost of the other workers around the card. So, if there are at least two other meeples (any color) next to the card (any edge), it would cost at least 8.