I thought I responded to this yesterday, but maybe I never hit submit. Prices are going to fall until people buy as much as they sell. Currently, the easiest way by far to make money is to sell resources. I don't know about you guys, but hunts, daily gifts, and forts combined make me significantly less money on a daily basis than selling resources do. On top of that, selling resources is a lot more predictable- I control how much money I make doing that, whereas getting zilch on a hunt after tying up 300+ units for 12 hours is frustrating and happens often.
Another way to look at this situation is that the demand for money far outstrips the demand for resources. One way to tip the balance is to remove oasis from the map, or fill the servers up more so more people are fighting for the same number of oasis, which increases the demand for resources. Another way is to increase the money production from hunts, increase the hourly rate of money from forts, or to some extent increase the daily gifts.
You could also implement an "NPC Price" for crops, but in my opinion, trying to control the price by tweaking the number and/or level of oasis is a much more interesting way to do it. Putting a price floor in will just make the game too mechanical. I do think the resource prices should be a bit higher than they are now as well. It seemed like when they were in the teens, the game seemed less tedious.
It doesn't appear to me that everyone plays smart either. It seems that all oasis are hunted equally, but really you should be going after lumber and iron, selling that, and then buying stone and crops when needed. Also realize that there is a huge price difference between 2 cents and 3 cents... 50% in fact! So when I see someone undercutting the 3 cent price with a large lot of 2 cent crops, I will buy the 2 cent crops and resell them at 3 cents, or just keep them- 2 cents is too damn cheap to pass up! This strategy is profitable until you hit 9 cents- anything above that, and the 10% transaction cost will eat up your gains. These markets could be pretty easily gamed as well, but until I successfully test that, I will keep that idea to myself

I could talk about this for hours, I work in trading, so its more than just a passing interest.