Well, let's see....if we take your numbers and plug them in with the percent of slaves that ended up in America (6%) and the slaves that ended up elsewhere (94%), we get approximately this:
About 6,110,000 slaves sold total, of which...
About 366,000-367,000 ended up in America.
Vs.
About 5,740,000 that the Yankee slave traders sold elsewhere.
That gives us about 5.4 million slaves that the Yankee traders profited from that were not sold in the South. Looks like the Yankee slave traders were getting the better end of the deal by far.
You do know that Americans were minor players in the slave trade, right? That British, Spanish and Portugese were far larger presences in the business?
Statistically, there were about 9 million slaves brought from Africa to the New World. Of those, 475,000 were on Spanish ships, 3.8 million on Portugese ships, 3 million on British ships, 544,000 on Dutch ships, 1.3 million on French ships and 366,000 on American ships. Americans were, admittedly, more in the business than the Danes, whose ships carried 100,000 slaves to the New World.
Another way to slice the data is to look at where the slave voyages originated. Analyzed that way, almost 5 million slaves were carried on voyages that set out from Europe, 433,000 on voyages out of the Caribbean, 3.2 million on voyages originating from Brazil, and 229,000 on voyages originating from North America.