It took me a bit to understand what the "cost" meant. So if I understand this right, the cost is also subtracted from the black hole size and each click drives up the cost until you get to the next stage when it resets? But it seemed to me like there was quite a bit of RNG involved as well. I literally "lost" on the second click once. Highest score I could get was 4,9 mil by only ever choosing the rightmost upgrade and ignoring the other two