I buy, fly, sell all within 10-20 minutes, does it change that quickly, or is the data just never that current?
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I'm using the figures in the commodities market itself, so I just set the destination, is there a setting for origin that I have missed?
This can happen when your Trade data isn't current (24hrs) or - AFAIK - at the start of a new daily BGS cycle. I've seen occasions where current Trade Data existed (traded well within 24hrs) but the Commodity Market didn't display the actual current Data after a new BGS cycle on the target System.
That incurred losses on an otherwise >500Cr/ton trade to my surprise more than once.
Only after docking (Trade data refreshed), returning and rechecking the Commodity Market, the projected Trade loss was correctly indicated in the market.
So in regard to BGS states, it seems it can display false (obsolete - last BGS State) Data from the target System unless new data can be purchased (impossible if data is less than 24hrs old) or physically docking at the Destination.
I believe that might be connected to a very old issue, where certain Commodities even went out of Supply due to a new Faction State going active but the Trade Data display didn't reflect that change at all - making the old Galaxy Map Trade Data at that time highly unreliable as well in regard to Commodities available vs. unavailable.
Overall though, luckily such occurrences are fairly rare and are cleared up in the market display no later than after a single bad trade at the destination.