I'm making a board game about constructing molecules out of elements. For example you can construct water out of 2 hydrogen and 1 oxygen. When a player constructs it they take a water card worth 6 points. However this currently has a diminishing return, the next player to construct water only get's 4 points, then 2 points, then 1 point. I felt it simulated a supply/demand system, where to more you supply the lower the value of the commodity becomes. I then asked myself, what if it was the other way around? Water is worth 1 point to begin with, then 2 points and so on. While this doesn't make sense with the supply/demand analogy it does create interesting decisions to think ahead.
Edit to make answers more objective: What are the pros and cons for each system? What games have these mechanics?
(the game is calle Entropy btw, you can read more about it here http://boardgamegeek.com/thread/1032958/wip-entropy-chemistry-and-chaos-2-4-players-pnp)