I've been playing the game for a few mounts and I find the concept great but lacking player interaction. Maybe I mist the idea of the offer hyperlink, but on way would be to contract supplying agreement with other players.
If one player is constantly producing a product, instead of sending the lot to the market once a while, he could post an offer stipulating the quantity, the quality, the frequency of delivery, starting and ending date of agreement.
On the other hand, if one player is desperately in need of a product, he could post a request for the same conditions mentioned above.
Once a player finds an offer or request that satisfies his needs, he send an invitation to the other player and negotiations can start. They negotiate on price and penalties if the above terms and conditions are not respected during the contract validity.
Of course, there would have to be an automatic function that allows the offering party to send the items to the requester. Once the products are received, the cash amount would be transferred to the offering party. If for some reasons the quantities or qualities of the products are not respected, than the offering player would be penalised according to the negotiated terms and conditions.
I think it would be a nice addition to the game.
Phantoman