Stone!
I do not want to be cryptic, but I couldn't help. I think people are seriously overlooking Splinterlands land. It is unfortunate, because there are so many other things that are happening in the game right now, that it is very difficult to keep focus, even for a large holder like me. The reasons are all interconnected.
- Land 1.75 with new natural resources: Wood, Stone, Iron
- Research and SPS production needing those new resources
- Conclave Arcana pack set launch, with new Black Foil card type
- Mid Night potion, which can only be created on Land, and requiring both Research points and those same natural resources

Out of all these the most valuable is Iron in terms of production difficulty. Followed by Stone and Wood.
However, this grain factor plot shows the fair value of each of the natural resources in terms of production difficulty. Notice, that stone is currently trading about 1.8 times its fair value. It doesn't means it is the most highly priced natural resources, but it is most expensive relatively speaking.

This plot above should help in understanding in terms of raw price which one is most expensive. 1000 iron is 444 DEC, and that is the most expensive natural resources in terms of price. But the reason stone is rallying so much is because there are not enough stone plots active.

All over Praetoria, people are producing a lot more iron than stone, in terms of natural resources. There are more PP on iron than stone. Plus Aura plots have super boosts, because people want to produce as many potions as possible, as quickly as possible. However, that consumes a lot of resources, including grain.
This is a curious plot. Not many people are familiar with it. This is the Net Production Plot of the resources. Anything positive here, we are creating a surplus stockpile. Anything negative we are depleting the existing stockpile. We all know that there are a lot of grain stockpile and its price is low. But at Praetoria, we are burning through 14M grain every day and increasing now.
So here is an advice. Prices are going to go up. This is a fact. If you don't have grain, start buying grain now, while it is still cheap.

It is a bummer that I don't produce enough stone. My whole region only have 9 stone plots and they are all common. So I am not going to win that battle. But at least I am stockpiling grain.
There you have it. I just bought another 9M Grain! I am burning through them very fast! A big famine in coming guys, get ready, otherwise there will be very little to feed you monsters!