Yes there is a lot of information on that 🤣

https://land.spl-stats.com/resource

Value of the resource in DEC:

And even more interesting is the grain factor chart... because every producing resource had relation on grain, so easy to say, this is to simple like this but is more a rule of thumb:
everything blow grain factor (gray line) is hoard everything about grain can be sold... if the market is perfect it would all end up on the 1x of grain (so on the gray line)