Build height is less to do with cost or complexity, and more to do with floating point accuracy. Try teleporting up to 100,000m or so (this is something only land owners and EMs can do) and using Firestorm's rezplat command to pop out a platform to stand on. Then look at your jellified self. That's the system struggling to cope with you being a very long way from <0,0,0>, with no way of using a floating origin like some systems use to work around it.

You also have the problem of many years of scripts all being built around a region size of 256x256. Now, I'd certainly like regions to be much more affordable to normal people, maybe to the degree where blobbing 4x4 regions together into a mini continent becomes viable. However even if the grid could cope with just dropping km-wide regions into place, the scripts that expect 256m on a side probably can't.

That said, maybe the Lab should charge for simulators instead of regions, and let people decide (up to a point) just how many regions the sim is running. :P

would be great but unfortunately the limitations of region sizes are a majority part in financing SL as a whole, it's the same reason the price to rent a dollar's worth of virtual dirt still runs in the hundreds of dollars a month as you're not really paying for the hardware but rather the exclusivity of the software itself.

i'd suggest checking out the wasteland regions, they've put teleporters all along the borders of their regions so that you're automatically teleported to a higher/lower layer when walking off the edge, and it makes for an enormous environment by SL standards.

Arduenn is correct. Sim sizes are not something that can be adjusted. However, if LL had an option for ultra low usage sims similar to old void sims was available, it would allow owners to do what you're describing. That would be a LOT of work on LL's end though.

Land prices are related to surface area, not to volume, so I don't think LL is going to go along with that. But one can always hope they'll prove me wrong.