Quote Originally Posted by MrGoodfellow View Post
But as for raising your stats... you pay what is written next to the + sign. If the stat has + 1001, and you click the button to make it 1003, then you just paid 1001 in money to raise your stat. The next click will cost you 1003, then 1005, and so forth.
To expand on this... Initially, the price increases by 2 per each update. However, once the price reaches 6005 (or a given stat is upgraded 2500 times) the price jumps to increase by 4 per each update.

Not sure if price increases jumps again down the line, didn't got that far yet.