Cost of Unlocking Building Slots

21/01/16 10:26
How does the cost of unlocking building slots go up?

My next slot is either about 19 million or 40 golden balls, when I use money it doesn't raise the amount of golden balls required for the next slot but it seems that when I use golden balls it does raise the amount of money & balls required for the next slot. Also does each slot always add 10 golden balls to the cost of the next slot when using them or is there a cap somewhere?

22/01/16 09:02
Each slot goes up by another 10 balls. Get playing tournaments !