In the 70's I can remember working on a VLCC
* carrying about 240,000 tons of oil from the Persian Gulf to Europe via the Cape of Good Hope. (Suez couldn't take a ship of that size and draft at the time.) It was about late September/early October and as we were ploughing up the coast of West Africa we got orders to pull into an inlet near Dakar, drop the hook and await further instructions. They estimated the wait would be about a month. No reason was given but the Old Man, who had worked for this particular oil company (one of the seven sisters
**) for some years, told me it was because the oil price per barrel usually climbed up as Winter approached, and this routine was not unusual.
There are about 7 barrels to a ton, so the ship carried about 1,700,000 barrels (I've melded long tons and metric tonnes here for the sake of clarity.) So if the price of a barrel goes up a few dollars, we're talking mega-money here. The cost of paying the ship's crew and other consumptions is pretty miniscule in this calculation.
*VLCC Very Large Crude Carrier also described as a Supertanker. They're double that size these days.
**I've deliberately not mentioned the ship's name which would give away the name of the Company. Last thing I want is button men coming after me.
In the end we were there about a fortnight, then got orders to kick
'Lands' End for Orders' into touch and fast steam for the LOOP (Louisiana Offshore Pipeline) so I figured a better deal had been made ... but that's another wheeling and dealing story.