You can buy 5.000 rares for 2.500 gold - that's the same prize as for the other resources.
But producing rares is twice as difficult. So you should get only 2.500 rares for 2.500 gold.
The research tree update has made this problem worse, because now rares are more precious in general.
But producing rares is twice as difficult. So you should get only 2.500 rares for 2.500 gold.
The research tree update has made this problem worse, because now rares are more precious in general.