Which is EXACTLY what Bk 7 is supposedly for.Or that the trade system was intended for players flying the tramp trade in 200 dT Free Traders and 400 dT subsidized liners, not for multi-billion-credit NPC corporations using 5000 dT freighters on main trade routes.
Bk 7 is for people like I was in 1988 - running corporate campaigns and needing to know what was reasonable. Mind you, the only way we made even that work was to limit the number of agents by the population of the world. We used Bk7 trade (well, MT Trade, actually, but it's almost identical), and limited the number of agents by population. (Pop^2, IIRC)
Thing is, big merchants (1200+ Td) existed well before Traveller had a trade system capable of handling it, and even Bk7 can't handle big ships above what Bk2 can generate without tweaking.