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In further as it stands one can build a 'mothball hangar' that would normally have an insane maintenance cost but can considerably cut down on the maintenance cost of other ships sitting in port, using one designed for the ship above we have:
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In your example, you build a hangar that costs ~4k bp in order to save ~1.5k MSP per year, while requiring an additional 4,123 tons of maintenance capacity.
Assuming you need to build two maintenance facilities (60BP each) to provide the extra capacity, and with MSP costing 0.25 BP each, your annual savings represents a rate of return on your investment of ~9.1% while occupying 100k workers.
You also have an up-front cost of the shipyard needed to build that carrier (~11k bp, depending on your tech level), and the ongoing workforce that yard requires (almost 10m workers).
You are going to have to make (and use) a lot of these carriers and/or wait a very long time to recoup the cost of that yard.
There are simpler ways to get far better returns in the game.
For example, suppose instead of building that shipyard you build financial centers of equivalent cost.
Let's say 90 fincens. Costs 10.8k bp, and 10.8k corbomite.
Uses only 4.5m workers. Less than half what the yard needs.
Returns annual income equal to 27 times your "wealth per million workers" tech level.
Even if you are still at the starting tech level (100 per million workers per year), and have no wealth creation bonus from your governor or sector, that's 2.7kbp per year.
So a bare minimum rate of return of 25%, using half as many workers.
With a couple tech levels and a modest governor bonus, it's not hard to be making your investment back in two years or less.
I think there's an argument for endgame gallicite starvation scenarios (esp with high-speed doctrines) for the cheapest "PDC" that is just a ton of hangar bays, just to convert some gallicite usage into not-gallicite usage, wealth costs be damned.
Also, ships in hangars still count towards maintenance tonnage?
EDIT: They don't, you were talking about the extra size of the "yard."
I think at early to mid game this is definitely NOT worth it, but again once you start hitting end-game techs if you haven't managed to spool up gallicite mining for whatever reason this can help mitigate gallicite consumption a little (you typically have near infinite duranium unless your ships are all giant armor bricks and even then neutronium bottlenecks first?). My ship of only a bit bigger size is 40k BP for 45kt, so a hangar that can store it is 6k BP and i'd save 9k MSP per year or about 900 gallicite per year in MSP cost, if i'm calculating this correctly.
My mining productivity is lagging a bit (50/yr) so that's 18 mines at 1x productivity, which, if automated, costs 4320 BP. For the sake of argument let's say it averages out at 1x between accessibility, gov bonus, and transportation latency/throughput.
Paying an extra 50% to conserve the same amount of minerals with much less micro (and I can go even cheaper on the PDC if necessary) isn't the worst deal. (Even if my numbers are off, gah. closer to 8k MSP and 800 gallicite which is 16 mines)
