The shipping regime is closer to that of the 17th C trade - where the shipper bought and sold the goods.
SPeculative trade is a very different beast from demand trade, at least from the standpoint of pre-rapid communication comparisons. It's MUCH riskier.
16th, 17th, and 18th C trade shows a very high rate of shipper-owned goods auctioned quayside. late 19th on, almost none of that. Difference? Transoceanic telegraphs.
So in a setting where getting anywhere takes a full week, where a return trip is going to be closer to two weeks, and where there is no communication faster than the fastest ship (maybe augmented by comms to vessels about to jump out beyond the limit and then transmitting just after jumping into a system), the earlier trade model you mentioned is going to be more likely than the latter.
Does anyone know if the cost of a vessel in comparison to prices that would've been paid for cargoes was, in the 16-18C, proportionally similar to that in the 3I? How viable is the mortgage period for a Beowulf or Empress Marava in comparison to back then? I like to imagine that with advanced financial services, stock and product production and consumption tracking and analysis systems, and at least the same amount of canny married to superior education that the Traveller free trader concept is at least reasonably feasible.