I think science and production are bound to fluctuate the most. Production gets REALLY expensive when wars are going on. Food really only goes sharply up or down if someone is being an idiot and buying/selling too much of it. (correct me if I'm wrong here

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Science, in my mind, should be a lot more valuable post-patch, because you can't rely on getting as much from mazes at once. If I see it for 200, and have any gold at all, that's pretty much an instant buy for me. I see it quite regularly sitting at 600 gold or so, but was conservative in my 300-500 estimate. But maybe my games so far have been more science-biased than other peoples. They certainly have been more about tech races then clobbering everyone with military.