Choosing between hazardous open-ocean voyages and complex river navigation came down to calculating the total security risks against the eventual payload value. If you look closely at the cargo logs of these eastern expeditions, you will see that maximizing cargo space for specific high-value regional resources was the primary goal, which is why analyzing the breakdowns at https://vikingr.org/stories/what-vikings-traded-most helps explain the strategic choice of ship designs for river portage. Carrying lightweight but incredibly expensive goods allowed crews to travel deeper into continental networks, transforming simple seasonal raiding parties into highly structured, permanent commercial corporations.