Everything is calculated in terms of risk/reward. Just as it would be profitable to take a 10/1 odds bet on an event that had a 12% chance of happening, so too does one decide to undock in highsec to move cargo.
As an example, let’s say you want to move 600M in bulky PI or Minerals in a JF because you can get an extra 200M shipping it elsewhere, should you?
Expected value outcome of selling locally: 600M - 0
Expected value outcome of exporting: 800M - [(800+HullValueOf10B)*P(Gank)]
Thus if the probability of getting ganked is greater than ~1% (180M), which it sure is, then making any and all shipments with this profit profile is a terribly ill-advised idea.
The probability of getting ganked in a freighter in Uedama or Niarja is at least 10%, probably more like 20%. Therefore, you need to have a shipment profit of over 2B to risk a 10B JF hull. Now, of course, for you to have a shipment profit of 2B, you probably need to move a stupid amount like 8B in cargo if we assume a rosy 25% margin, which itself vastly increases the probability of getting ganked to probably over 50% in the first place and therefore, it behooves the capsuleer to never go through these systems. The irony of the situation is that keeping cargo value below 1B is counterproductive for the freighter pilots who ought to be doing something else with their lives because it doesn’t reduce gank risk nearly enough to compensate for the fact that the pinata of a hull that is risked costs 9-10B.
Btw, you can simply reduce these isk numbers by roughly factor of 10 to get the equivalent numbers for a vanilla T1 freighter.
All in all, it’s best to sell all of the risk to someone else via contracts until courier contract prices rise to meet the exhorbitant risk that comes with their chosen vocation.