When trying to optimize buy/sell to get an edge in the early stages of a match, I found myself many times writing down the price I bought a resource so I could remember it and estimate how much I would make if I sold it at the current market price.
It would be interesting to show the price of your last transaction for that resource and the difference to the current price, so you can quickly estimate how much money you're making or losing if you go ahead with the transaction. Maybe the hover popup for the buy/sell buttons is a good place (show last buy in the sell button, and viceversa).
