You can use the formula: =CEILING(Ships*20 / (500 + Upgrades*20)) to compute the minimum number of ships you'd have to buy to generate the same increase in capacity.
You can then use =SUMPRODUCT(3 * (4500 * 1.03^(ROW(INDIRECT(Ships+1 & ":" & Ships + Ceiling))) - 4475)) to compute the total gold cost of buying ships.
But for upgrades you'd have to manually plug in each upgrade cost and I want a formula that computes it dynamically.
So, in the end I ended up making a simple version here: https://docs.google.com/spread…KH3IIick/edit?usp=sharing but it requires you inputting the price of the upgrades instead of computing the price dynamically, which is what I'd prefer.
The example price is also with Optician 50, and ideally, you'd put the level of Optician in the formula.
But the point was that I wanted someone else to make this, not me.