Agreed. I think this needs to be a mission often seen in stations with huge demand for commodities. Especially Terraforming worlds and recreational outdoor worlds (Tourism).
From the initial release of this game I've felt that since the economy doesn't function with persistent supplies, that an open commodity board setup for trade was a miss. It should be removed and everything trade-wise should become courier missions and/or special purchase/sell requests. The amounts you would be offered would be dependent on your trade rank, reputation with local factions, local economy, etc.. Anywhere from 5 tons to 10,000.