The labor theory of value is really, basically, the first step. It gives us the coarsest view of the cost of things. We can then consider rarity of the materials involved, and then we can potentially consider the quality of the craftsmanship. The concept of starting simply is something of a religion around here, because these systems can get out of hand so quickly. We'll iterate on it as soon as it becomes obvious that it's the next step that will return the highest value, and i am very expectant that that'll happen at least once.
Modding is something we've been talking a lot about lately. Specifically, one thing I'm really worried about is that we could send out a few copies for internal beta, then those guys start modding a living and unfinished code-base, and suddenly we have to support decisions that were bad ones or made accidentally.
This is a horrible nightmare of a trap that leads you to things like Microsoft's 30 year code bloat. It's horrible. I can't stress how bad this is.
To get away from this, at this point, our plan is to carefully consider and harden a small number of systems that the mod community can access, and only condone mods for those systems. We will then slowly grow this list as we gain confidence in the robustness of the design of the other areas, and we will make this information public. You could mod the other stuff if you really wanted to, but the chances that your mod would need to be patched as we patched the game would be quite high, and we want people who want do this to know what they're signing up for.
I can tell you that, technically speaking, the entire game state, outside of the actual terrain itself, lives in scripts. In a perfect world where we have the time to harden every system, you will be able to add new commodities, new character behaviors, new models, new animations, everything but (probably) the terrain itself will be moddable. You could make a zombie/alien/cow survival tower defense on the Clockwork Empires engine, and it wouldn't be all that hard.
The usual disclaimer. EVERYTHING said here is subject to change. Don't want to upset anyone if things change, but these are our intentions, not hard facts.
Edit: Oh, yeah, people will own things, but not very many things.