I like the idea for this :O
i agree that an inverse system should be in place in regards to maintenance costs..
think of it like an upside down triangle with the point facing down V
lets have a look at streets for instance... the very earliest streets were dirt..
Now dirt streets require little or no maintance
Creation costs: Nil clear the area you want for a street tamp it down and your done...
Maintance basics: Applying water to the dirt to keep it compact (depends on climate (dry), Having duckboards (depends on climate (wet), Drainage (depends on climate (really wet) and the occasional beating the ground (if water is short) and some cleaning mostly to do with animals... but thats about it.... simple to make simple to maintan
the next level of streets were cobbled or paved with stones not always cut, faced etc
Creation costs: The quarrying.. i say quarrying with an open mind... it could just be picking up allready flat rocks, slate, shale, limestone which sometimes turn up in nice flat forms or it could be hacking out living rock with rock chisels and water... in other words labour heavy and a general pain in the ass to get barring natrual accidents and laying well lets not get started on that...
Maintance basics: Keeping them clean, free of mould (depends on climate (wet), animal faeces (depends on civilization), keeping them level (depends on the ground that you have laid them on), regrouting them (depends on what your using to grout them...) and then every ten or so years you need to pull them up and reset the whole damm thing... clean the stones/pavers regrout relay and repeat...
the next level of streets would be a variation of that... cobbled or paved with a side walk (if you have pack animals) and drainage (if you have a sufficently large population), sufficent central planning and the inclines to carry the waste out (if you the drainage is good enough to warrent it...)
Creation costs: More cobbles/pavers and if you want to have proper drainage you need finer cobbles/pavers and a fine grout to keep the water in there... heres the kicker the other 2 could be carried out without large scale central planning (gennerally) this requires a concertated effort as does orentating the inclines correctly...
Maintance: all of the stuff you need to do with the cobbled or paved stuff... a side walk needs to be kept clean and the drainage canals etc need to be routinaly cleaned and kept clear of debris and blockages... no one wants a drain to back up and spew whatever the contents of that are...
Pretty much everything in civilization should get more expensive as time goes on... but also the rate at which capital is generated should increase as well... now the interesting thing is that things like food production do increase but only in percentages e.g This new strain of wheat increased the yeild by 25%... whereas population increases exponentionally...
All im saying is that i agree that things should increase in maintance costs as the game goes on... as should the amount of military units that one can have in the field... making it an almost imperitive to increase the capital generated... but this should be offset by the costs of civics and the like...
Another Masada Rant Over (AMRO)