I want to create some ROI tools on my game for personal analysis.
Let's say that I have 3 different level of special powers with a recursive cost and certain bonus. So, I want to see when certain level will start have income.
1st example: 1000 coins for 10 uses. Bonus: +10% on farming speed. 2000 coins for 10 uses. Bonus: +20% on farming speed. Etc
In this example, I know exactly what the bonus will do. I have the price of the farming per unit and I can calculate the income per use for each power level. So, I can tweak the numbers using the ROI tool to make the effect better.
2nd example: 1000 coins for 3 power ups on a weapon. Bonus: +1 attack power, +5% chance to destroy the weapon. 2000 coins for 3 power ups on a weapon. Bonus: +2 attacking power, 10% chance to destroy the weapon.
3rd example: 1000 coins per use. Bonus: 30% heal, 5% chance to get injured. 2000 coins per use. Bonus: 50% heal, 10% chance to get injured.
As you can see, the first example is simple to calculate the income vs cost. However, the second and third example don't have an exact effect and both of them have a probability to either good or bad effect. How do you work on this type of ROI? How do you calculate the pros of each level?