I've had a brief look around in the past and was never able to find the formula that roughly determines how base production is calculated. Now that we're thinking about upgrading our base to a level 5, I'd really like an idea of how it works so I can plan out the optimum special space use (and whether or not I should buy extenders for the special space). Is there a topic that covers this already? How does it work?

Its (What you get from Structures)*(1+Base Abilities)*(1+Availability)*(1+Base Level Bonus)*(1+Base Defender Bonus)*(1+Loyalty Bonus)=what you get

If you don't get what the 1+ is for it's because it's all + % , So if you get +20% form Base Abilities you have to times it by 1.2 to get the new outcome or Base Level Bonus of a level 5 being 2000% you would times it by 21.

Have in mind that no one is hunting level 4 bases actively.. but once you reach level 5 things will get a lot different. And so if you want to protect your base your upkeep will jump to the sky.

We have a tough 6 with fully fitted out normal space - 9.6bill upkeep- it gets very expensive