It's either a very strange future we inhabit or technology didn't advance too well on communicating with other systems. Surely it is possible to communicate with known contacts in distant stations to set up deals for commodities, get a price and fix the deal before leaving dock? I'm not talking missions, I'm talking setting deals with stations you've previously visited or have good reputation with the controlling faction and pricing the journey before you leave. Obviously these trades would have time deadlines on them at which point your sale price reduces, cutting profits or even expiring leaving you to risk general market prices at the time or worse, leave you unable to sell.