How about turning the trade depot into an auction house? It could work like this:
1. You search for the item you are looking to buy (type it in, select from a list, etc)
2. It shows you how many of that item are currently being offered up for sale. (Lets say 500 nails are currently for sale on the market)
3. A 30 second auction runs. You place a bid and whoever bids the highest in the next 30 seconds wins the item(s). You are bidding a § amount on a quantity of the item. You bid against other players desiring the same quantity (lot size). For example: You bid §40 for 10 Nails, any other player looking to buy 10 Nails at that time places their bid. If in the next 30 seconds your §40 is the highest, you win. If another player bids §50, they win. There should be a cap on the lot size to keep it simple, (ie. You can't bid on more than 10 of an item at a time.) As for the sellers, items are put up for sale in the order they were posted.
Now that they sold, there are only 490 Nails on the market until someone posts more up for sale. As the quantity available of a particular item diminishes the bids will increase naturally. Supply and demand. A minimum (starting bid) should be determined for each item (to protect the seller) Maybe base it on averge price paid?
Right now the trade depot is terrible. It is almost impossible to buy anything. Items are almost always already sold out by the time you click on it and you are taken to that players depot. Also, as for the sellers, there is no reason to sell an item below the maximum price.
