//edit: I might have a slight calculation error in it. Will have to check. The general message: it takes freaking long remains.
It's a fact that building and destroying a POB is in no relation to each other.
Let's have some numbers here:
A base becomes useful at Core 2 and a real thing only at Core 3 or higher. Therefore you have to have for example:
Core 1: Shield (60.000) + 1 Storage Unit (95.000) + Core upgrade (420.000) = 575.000 units to have a shielded Core 1. Core 2: 1 Storage Unit (95.000) + Defense unit (80.000) + Core upgrade (420.000) = 1.170.000 units for a small mining base Core 3: 1 Storage Unit (95.000) + Defense unit (80.000) + Core upgrade (420.000) = 1.765.000 units for a useful mining base
Statistically, I would guess that most flights for POBs are 1,5 systems, or roughly 50-70 k for average POB positions, and a lot longer for sub-optimal positions. As there are some hard-to-get commodities in each build, I guess an average of 8 minutes per flight - which is likely rather an optimistic pick.
This Mining POB of 1,765.000 units would need 353 flights with a pure 5ker. Let's assume the average flight time is 8 minutes:
353 flights x 8 minutes = 2842 minutes = 47,1 of pure hours of flight time for a Core 3 base that can go on to Core 4.
These are pure building times!
There is no maintainance done yet.
A base needs 2 flights per day.
So, you invest a lot of time. A LOT.
And destroying (of a Core 2) takes how many Battleships? A few. Rather easily manageable for a determined group. Then a Core 2 base (that took 234 flights of a 5ker to build, and roughly therefore needed 1872 minutes or 31 hours to build. Without maintainance!) can be destroyed in less than 1 hour of shooting.
Even the Core 1 that you kill easily took around 15 straight flight hours to build (assuming you kill it before it gets the Core upgrade finished, which is when most Core 1s die).
I'll just mention the monetary side, but won't do calculations. Just one thing: If you want to do Core upgrades in a reasonable time, you have to offer interesting prices and this costs you around 500.000.000 per core upgrade. Of course you can do it on your own, but then you will never get anywhere in a reasonable time frame.
So... comparing the cost, and especially the time it takes to build, and the effort it takes to destroy it, I think everybody can see that the system is very much in favour of the attacker who loses 1 hour, perhaps 2 hours, in comparison to time spans between 10- and 30-fold.
Yes, we need a different system. Either bases need to be MUCH easier to build (like... cut the hauling requirements by 2/3) or they have to be really hard to destroy, with a heavy cost and some real risk on the attackers' side.
How this can be done?
I do not know.
But I think some sober numbers help to show how badly the system is in favour of attackers.