You don't need to predict price changes. You just need to predict that the price will not change in the next 4 hours. Example: Pear tree seeds: min: 9500, mid: 10000, max:10500 You decide to "test the waters", and put in a buy offer for one seed for 10000. You wait a minute, and conclude that the item is "on the rise" and therefore you must offer above mid. You cancel the offer. You put a new offer in at max, 10500. It sells instantly for 10450. This tells you that the item is not bought out, so it is possible to buy at a lower price than max. So you put in a buy offer for 999 more seeds at 10005 each. After about 10 minutes, the offer resolves. You now put them in for sale at 10490. You log back in 6 hours later and they all sold.