If you haven't seen this thread (which I suggest you should) then all you need to know is that I recently finished a large automatic potato farm, and am selling all of the potatoes from it. 6/15/16: 868,080 potatoes sold, and 53,528r of profit has been made by this farm. To get to the potatoes, all you need to do is /v 5172 and walk into one of these: and it will take you to the area to buy the potatoes. Currently the prices for the potatoes are 1 stack for 4 rupees ! Check out this thread if you're curious as to how the farm works. And while you're there, feel free to buy some pumpkins, produced by my overly large automatic pumpkin farm, which you can learn about here!
Using shavingfoam's EMC Shopkeeper tool, I found that I have sold 382,624 pumpkins, which is 24,848 rupees! I have also sold 81,472 potatoes, which is 4,256 rupees!
Bump. I currently have over 7 double chests of potatoes in stock. Since this farm has opened I have sold over 713,000 potatoes, which is about 43,000r of profit.