As I've said before, using 250% gold card will increase the income capacity of the capital to 20. Increasing your production queue to 20 since unit production is dependent on how much the country is earning.
Yes, it is dependent on luck, and utilizing your resources well, so it might have been intentional on the part of the developers hence the question mark above.
There is a further problem with this - there are more than 2 gold boost cards (1 turn and 2 turn which have no real difference as both work for one), all of which can be stacked with each other, but there is good news, strategic building is limited at a mere 144units per country per turn and getting them all means a lot of luck or parliaments the latter will mean they are rather weak until they pull it off.
As such I must really recommend that all but maybe 2 of types of gold card be removed or make them based off the base/mine value and not the total value.
Oh and trying to exceed 1000g on a country (8 + mine + cards) will result in a ctd.