I kinda meant the costs more, as the upgrades being multiplicative is somewhat obvious (to those who code)
Upgrade costs are multiplicative as well. A lot of them are just multiplying itself by 1.5 or 2, but some are 3, 6.5, or 10. And then a few of them modify above a certain threshold, like the first power upgrade cost multiplier doubles from 1.5x to 3x once the cost is equal or above 1e6.
The upgrades that weren't as powerful (base and mult) actually have their cost multipliers shrink when the exponent is above 6, 7, or 9, since I didn't want then to feel as useless later on.
I can go into more detail if you'd like me to.
There is also a good bit of rounding so as the numbers get bigger there is definitely potential for it not being fully accurate.