When selling, it first compensates for the increase in whatever youre selling, THEN pays you the lesser amount. However, when buying, it first compensates for the decrease of the item, then gives it to you. Therefore, if I were to sell 1 diamond at 250, it would say "Buying 1 diamond at 300!"

But were i to sell at 250, it would say "Selling 1 diamond at 200!"
 
This is just an example, but you get the problem. Please either make them both sell THEN revalue or both revalue THEN sell, so that people can make at least something off stock market type trade. Otherwise you either lose tons or barely break even, it's really annoying, thank you.