I also agree, and agree that making the materials more expensive but requiring less is the best way to reduce the work but prevent too many pob's from flooding areas.
Not sure about those initial numbers, I have found that if you build near a cheap alloy supply, you can build and build a level 1 mod, with shield and storage for fairly cheap, its just the time to collect everything that slows you down. Once you're set up the alloy to maintain it is cheap, but all you can do is bring it in as much as possible to keep up with it (unless you have a barge at your disposal).
Simply increase the value of something like reinforced alloy, and reduce its necessity to say 1000 a day, would reduce time needed to maintain it, and you could use that time flying, however you like, to make the cash for the base.
It even seems to me that if you have full crew, and keep them supplied, you shouldn't even need alloy to maintain it, and it should only need alloy for when attacked or if you build in a high radiation zone.
That way maybe the value of things like Oxygen, water and food rations could also go up a bit, and it would be those commodities you'd worry about keeping on the base, for the people, which definitely do need them to survive.
A well constructed base would not just degrade, keeping people alive on them would be the maintaining factor. If it were just the human commodities that were used over time, it would actually provoke people to extract their own oxygen and water from known areas to make it cheaper or easier to supply.