The Lands SPL website sports a new alert at the player overview dashboard. It is fairly sleek and timely. If you are not living under a rock (stone), you probably know that Stone prices are falling at Praetoria for a while. Now that the grain prices rallied a lot due to the land card sales (and remained higher), it cost more grain to mine stone, than its price if you sell it.
If you click on that yellow highlighted box, you will get a list of plot that are currently in negative ROI.
When I click on it, it shows that most of my stone plots are DEC negative currently. As I have mentioned many times in the past. I am generally deficient in stone. In Region 10, Highmoor, I only have 9 total stone plots out of 1000 plots. I have purchased a few stone plots in Quegmoor, but the extra stone production there need to be transferred into Region 10, so that is not easy and costs money. So I typically buy and keep a stash of stone handy in Highmoor.
A lot of my stone plots are common plots with common cards, so basically very plain vanilla. Obviously I expected them to be negative. The example is below.
The good news is, it doesn't matter even if the card PP is higher. This is because higher PP cards require more grain than lower PP cards. The two plots above are commons with no boosts (other than terrain boosts) and they have 10K base PP each, and they are negative.
The two plots above are also common, but sports 24K and 30K base PP, 3X the previous plots, and they are worse! :)
So, in order to get positive on stone, you need a rare or better plot, and perhaps a rare totem and above boost. If you do not have a plot like that running already, probably not worth it to start a new one or buy a new one. It is cheaper to buy stone from the market, which is what I did.