My stand was (and probably still is) mistaken for a lack of willingness to flesh out a prototype. The fact is that I an not willing to flesh out a prototype specifically for the sake of demonstration.
It can be argued that a prototype specifically for demonstration, would be work done towards your project (as experience if nothing else) and can ultimately be used within the final product. But as you so elegantly put it, demonstration of the material kind are expensive and time consuming. So much so, that the scope/scale of something as I wish to develop, would not allow it and could quite possibly rendering it pointless. The amount of time and effort I'd spend even producing a prototype could easily cause an overlap of technology, cultural relevance, fall steeply under the trend curve as well as be out developed by up and coming concepts.
I think you underestimate the value of a prototype.
A prototype can tell you many things, and most importantly of all, it tells you things before you invest too much into them. Rather than developing a whole game and then finding out that several core features suck, you can throw together some quick and dirty minigames that demonstrate the core features and prove that they are a) feasible to develop and b) entertaining enough to justify their inclusion in the game. The more atypical the feature, the more important this is.
If you don't want to develop prototypes because your features are so complex that it would take "too long", that to me is a pretty clear sign that your features are not feasible for you to implement. In a way, the prototype has done it's job without even having to write it - it's just up to you to accept what it's telling you.